The Speaker of the Commons, Michael Martin, is likely to be called before the powerful Wicks Committee on Standards in Public Life to give evidence into allegations that he had undermined Elizabeth Filkin.
The former ministers Keith Vaz and Peter Mandelson, who have both been subject to investigations by the outgoing anti-sleaze watchdog, could also be invited to give evidence to the inquiry into whether she was subjected to a "whispering campaign" by hostile MPs.
Sir Nigel Wicks, who heads the committee, will investigate the refusal by the Commons Commission to reappoint Mrs Filkin, who wrote a furious resignation letter on Tuesday.
A spokesman for the committee said: "We can invite anyone we like to give evidence. We will be looking at her tenure and whether people sought to compromise her independent role."
Mr Martin said it had been a matter of "great regret" that Mrs Filkin's letter – which accused Mr Martin of undermining her – had been made public.
The Speaker, who yesterday chaired an emergency meeting of the the Commission, called for details of the "pressure" put on her to stall her inquiries to be made known. "I will be expressing my surprise that she did not raise these concerns with me at one of our regular meetings," he said.
The Tory leader, Iain Duncan Smith, challenged the Prime Minister to launch an investigation into her treatment. But Mr Blair refused to defend the sleaze watchdog and said the matter "should be dealt with by the House in the proper way".
But Tony Wright, the Labour chairman of the Commons Administration Committee, expressed deep unease with her treatment and said his committee would today discuss if it could launch an inquiry.
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