Senior Conservatives have joined the party's anti-sleaze watchdogs in putting the spotlight on Mr Hague's refusal to order an inquiry into the long-running doubts about Lord Archer.
The head of the Ethics and Integrity Committee hit back at criticism from Tory MPs who believe it should have intervened to question his fitness to be the party's standard bearer in London. The three-member committee insisted that, under the Tories' rules, it could not decide to launch an inquiry into whether a member had brought the party into disrepute.
The rules state that it can consider only those cases referred to it by the party's leader and its governing board, which is headed by the Conservatives' chairman, Michael Ancram.
One senior Tory said yesterday: "A lot of MPs are running around blaming the Ethics Committee. But the truth is that William Hague has only himself to blame for not calling it in to investigate Archer. Under the rules, that is his job."
Elizabeth Appleby, the QC who chairs the independent watchdog, said: "The attack on the Ethics and Integrity Committee has no substance."
She dismissed as "abusive" speculation that her group had launched a "cursory" inquiry that had cleared Lord Archer after a complaint about him by Sir Timothy Kitson, a former party whip.
"The committee has no jurisdiction to consider a complaint about Lord Archer from Sir Timothy Kitson," Ms Appleby said. "Only a complaint that has been referred by the leader of the party or the board of the party can be considered by the committee."
Ms Appleby's staunch defence of the watchdog - set up by Mr Hague in 1997 as a key element of his crackdown on "Tory sleaze" - will add to the Conservative leader's embarrassment over the Archer affair. Some Tory MPs now want the committee to be given new powers to launch investigations on its own account. "Hague made a big mistake in the way he set it up," said one.
Senior Tory sources said last night the committee would not decide until next week whether to summon Lord Archer to appear before it. The group has already met to consider written evidence from Mr Ancram, who is claiming that he was misled when Lord Archer told him this summer that there were no more "skeletons in his cupboard".
It has requested written evidence from Lord Archer and will decide after studying that submission whether to invite the millionaire novelist to appear before them. The inquiry is widely expected to lead to his expulsion from the Conservative Party.