The man who brought down Labour's first all-women shortlists has vowed to do so again.

Dr Peter Jepson, who took Labour's all-women shortlists to an employment tribunal in 1996, says he is prepared to challenge new laws being introduced by ministers.

Jepson, an expert specialising in discrimination law, believes legislation currently before parliament is flawed and has vowed to challenge it, or assist with a challenge, if it becomes law.

He says shortlists which specify gender will fall foul of the EU's Equal Treatment Directive. Should Labour proceed, he says he will put himself forward as a candidate for an all-women list and take up the challenge when he is excluded.

"I've done it before and believe it or not I'd be prepared to do it again. Say I wish to become a local councillor, I will apply to be considered for an all-women shortlist and they will reject me - because I am a male," he said. "And then I will bring a challenge - not just against the Labour Party. I will say that the government has failed to bring about its legal obligations under the Equal Treatment Directive".

According to Jepson, the government's Sex Discrimination (Election Candidates) Bill will collapse if it is proved that it is a vehicle which could be used to introduce controversial all-women shortlists. He dismissed government claims that there will be no legal problem providing "positive action is proportionate to the issue".

Says Jepson: "Excluding all men or all women has no element of proportionality. The government is claiming this is positive action when it is actually positive discrimination. There is a difference - positive action, such as advertising in women's magazines, is legal - whilst positive discrimination is not."

He says the government is deliberately avoiding saying that the bill will be used to introduce all-women lists in order to stop him starting a judicial review.

"Stephen Byers is refusing positively to say that this will enable the provision of all-women shortlists. The moment he says that we can challenge it in judicial review," he said. "That would be a quick resolution - we could test whether I am right or whether the government is right."

Jepson claims senior ministers, including the Lord Chancellor, are aware of the flaws in the legislation and says the issue will damage Labour in the run up to the next general election. He says the government should let him challenge the bill now - or face months of uncertainty over the legality of its selections.

"If you bring a challenge against the government as well as the party then it is inevitable that it will be referred to the European Court of Justice and it will be dragged out through the press right up to the general election - that would be bad," he said.

A spokesman for the Cabinet Office said it would be up to the political parties to deal with the issue in their own individual ways.

"The aim of the bill is to reduce inequality between men and women. The purpose of the legislation is permissive and it is up to the parties themselves to decide what positive action, if any they want to take," she said.