The senior EPA official also scouted flats for her boss in some of Washington’s hippest neighbourhoods, and helped arrange his family trip to California over the New Year’s holiday so that the Pruitts could watch the Oklahoma Sooners college football team play in the Rose Bowl.

The push by Pruitt to enlist a subordinate in his quest for cheap bedding – outlined in a letter Monday from two of the top Democrats on the House Oversight and Government Reform Committee, Elijah Cummings of Maryland and Gerald Connolly of Virginia, to the panel’s chairman, Trey Gowdy, a South Carolina Republican – was one of several efforts he has made to minimise his personal expenses since moving to Washington.

Last year he instructed aides to arrange work-related trips in August so that he could either be on the road or working from his home in Tulsa, Oklahoma, according to two former EPA employees, rather than pay for a flat rental in Washington that month.

The Oversight and Government Reform Committee is conducting an inquiry into several spending and management decisions Pruitt has made since taking the helm of the EPA, including his decision to travel first class (because of what he deemed a security precaution) until earlier this year and an unusual rental arrangement he struck with a Washington lobbyist early last year, in which he paid US$50 a night to stay at her Capitol Hill condo for nearly six months, but only on the nights when he slept there.

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Citing the new information that surfaced during Hupp’s interview, Cummings and Gowdy asked that the chairman “issue a subpoena to obtain documents that are currently being withheld by the Environmental Protection Agency (EPA) relating to Administrator Scott Pruitt’s multiple abuses of authority in using agency staff for his own personal purposes”.

“If Ms. Hupp’s statements to the committee are accurate, Administrator Pruitt crossed a very clear line and must be held accountable,” they added.

Asked about the matter Monday, EPA spokesman Jahan Wilcox said in an email, “We are working diligently with Chairman Gowdy and are in full cooperation in providing the committee with the necessary documents, travel vouchers, receipts and witnesses to his inquiries.”

Hupp described her work for Pruitt on an array of personal tasks, including booking non-work flights with his personal credit card, during a closed-door interview with Republican and Democratic aides from the House panel on May 18.

Hupp said that she recalled Pruitt “has spoken with someone at the Trump hotel who had indicated there could be a mattress he could purchase, an old mattress he could purchase,” and that the administrator “had expressed interest in securing a matter” to her.

Hupp said that she did not recall what resulted from the inquiry, but asked to confirm that “it was not for use at EPA,” she replied, “Not to my knowledge.”

Gowdy could not be reached for comment Monday morning.

While staff members at the Trump International Hotel, which is located just yards away from EPA headquarters, make it possible for guests to buy Trump-branded furnishings, it does not appear to sell used mattresses.

A receptionist last week referred a Washington Post reporter to Tempur-Sealy corporate offices, which sells the same mattresses on offer at the Trump Hotel by mail order.

A standard queen mattress, without a box spring or any other accompanying items, costs US$1,399 before tax and shipping. A standard king mattress costs US$1,750.

Trump-branded mattresses used to be available more widely when they were manufactured by Serta and sold in department stores such as Macy’s.

But Serta, along with other companies that had paid to license Donald Trump’s name, halted that merchandising business during the 2016 presidential campaign. Serta terminated its partnership in July 2015.

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Hupp initially contacted the managing director of the hotel by phone on September 14 about getting a used mattress, according to emails released under a Freedom of Information Act request by the Sierra Club, rather than explaining her objective in writing.

In an email that day, Hupp identified herself one of Pruitt’s employees and said she was “hopeful you could give me a quick call when you have a couple minutes”.

The hotel’s managing director, Mickael Damelincourt, then connected Hupp with his executive assistant, Mary Hapner, to follow up on the matter.

Among the other personal tasks Hupp told congressional investigators she performed for Pruitt, she said she “assisted him in booking travel to the Rose Bowl” over his winter holiday with his family.

She also provided the committee with new details on how she conducted a housing search for him “over the course of a couple of months,” which ultimately entailed moves that Pruitt and his wife made to two separate flats in Washington.

While the administrator testified before a House panel that Hupp performed the flat hunt “on personal time”, Hupp said she did some of it during work hours and used her official agency email at times.

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“He asked my help in seeking housing, yes,” she said, adding that she was not compensated for this service.

Pruitt described Hupp in his congressional testimony as “a long-time friend”, and she told congressional investigators. “I would consider him a friend of mine, yes.”

However, government rules still prohibit a federal employee from making “a donation or a gift to an official superior” and bar a federal official from accepting “a gift from an employee receiving less pay than himself”.

Asked if she took leave from work when she looked occasionally during office hours to look at properties for the administrator and his wife, Hupp told committee staffers, “I did not.”