'Frankly, we think this would be an irresponsible act by the government, as well as by community leaders, including some legislators who would rather bury their heads in the sand without attempting to take part in a sensible debate on the matter,' Mr Tang said in a letter to the media.

He was responding to a call by Liberal Party chairman James Tien Pei-chun who, in columns published in several newspapers yesterday, called for an immediate halt to the nine-month consultation.

In a column in the South China Morning Post, Mr Tien said it was the financial secretary's duty not to introduce a GST because the Basic Law said the government should keep its expenditure within revenue limits, rather than spending first and then seeking revenue.

'Consider our huge fiscal reserve, the annual investment return on the Exchange Fund and a continuing programme of sensible cost-cutting ... I see no need to broaden our tax base from 1.1 million to 7 million people through a GST,' Mr Tien wrote.

Mr Tang said he was flabbergasted Mr Tien thought using the Exchange Fund - which underpinned the city's monetary base and the stability of the currency's peg to the US dollar - would be considered a viable and responsible way to deal with any future economic downturn.

'Using reserves to top up a deficit doesn't help to solve the problem of why we have a deficit in the first place,' he wrote.

Political parties and social groups plan to launch a campaign next month to seek support and donations from GST opponents.