Former housing chief Leung joined a New World Development subsidiary with the bureau's approval in 2008 but quit amid claims of a possible conflict of interest.

An investigation brought a promise of tighter rules on jobs for retired civil servants.

Chun, who wrote an open letter 10 days ago criticising the government for its overly cautious approach when screening retired officials' job applications in the wake of the Leung affair, believed he had been punished by Civil Service Secretary Denise Yue Chung-yee for speaking his mind.

'The only explanation I could think of is that this is an unconscionable use of power as a means to penalise me for daring to challenge her authority,' Chun said in his second open letter.

Chun, who wants to join casino magnate Stanley Ho Hung-sun's Shun Tak-China Travel Ship Management, had said he could not start work until October 3 this year at the earliest. Chun received the notice of the approval period's extension two days after his first letter.

The Civil Service Bureau did not explain the rationale behind the decision in the first notice and only gave a reason more than a week later, saying that it was down to the close business relationship between Shun Tak-China Travel Ship and the Marine Department.

But Chun remained unconvinced. He felt he had been picked out to be made an example, given that his new job was different from his previous one, which he said mainly involved dealing with professional or technical matters and did not touch on any sensitive issues.

'It is obviously not a reasonable reply because such concern has already been more than adequately addressed by one of the approval conditions i.e. I should not personally deal with or contact Marine Department officials over business of my employer,' he said.

The former marine official has been highly critical of what he believes is the government's foot-dragging in screening job applications by retired officials.

Chun claimed they were made to suffer because the government wanted to appease the public following the Leung affair.

Chun yesterday said he wanted Yue to explain exactly why he had to sit out such a long period.

'I think there are grounds for me to ignore such unreasonable condition in the approval and to lodge a formal complaint to the Chief Executive on the abuse of power and unfair treatment,' he said. The Civil Service Bureau said last night that six months was the minimum period required for Chun's ranking and it could set a longer period if necessary.