A millionaire businessman has won the right to make a High Court challenge to try to force the Prime Minister to call a referendum on the European Union reform treaty.

Stuart Wheeler says that Gordon Brown should honour the pledge that Labour made at the general election to hold a referendum on the EU constitution, despite the document no longer being regarded by the Government as one. Mr Justice Owen ruled yesterday that Mr Wheeler had an “arguable case” and granted him permission to seek a judicial review. The hearing will be held next month.

Mr Wheeler, a big Conservative donor, said: “I am absolutely delighted. It's clear to me that we have a very, very strong moral case for a referendum. What this hearing was about was whether we had an arguable legal case. From what I've seen of the judgment, not only do we have an arguable, but a rather strongly arguable case.”

The Conservatives said that they would call for the debate on the treaty-enabling Bill in the Lords, where it is currently under consideration, to be put on hold pending the review.

In its 2005 manifesto Labour pledged a referendum on the EU constitutional treaty. However, other EU countries voted “no” to the treaty, and so leaders of EU countries instead came up with the Lisbon reform treaty. Mr Wheeler claims that the British public is entitled to vote on the Lisbon treaty because, he says, it is virtually identical to the constitution on which a referendum was promised.

Rabinder Singh, QC, applying on behalf of Mr Wheeler for permission to seek judicial review, said that the application was based “on the underlying fundamental principles of good administration, fair play and straight dealing with the public”.

The Government had given an “unequivocal and repeated” promise to consult the British people on whether the UK should ratify the Constitutional Treaty — the substance of which was replicated in the Lisbon treaty.

He asked: “What's in a name when the substance is the same?”

Philip Sales, QC, appearing for the Office of the Prime Minister, said Mr Wheeler's case was “not properly arguable”. He argued that Mr Wheeler's claim was “misconceived” because the ratification of an international treaty was not a matter open to challenge in the High Court, and such a challenge would breach parliamentary privilege.

The judge rejected Mr Sales's submissions. He said: “In my judgment it is arguable that the claim, couched in the narrow terms that it is, does not amount to a violation of parliamentary privilege.”

Mr Singh claimed that the promise made in relation to the constitutional treaty extended “by implication to any document with a different name having equivalent effect”.

The judge ruled: “He [Mr Singh] submits that the court will be concerned with substance not form, and that if, as he asserts, it be the case that there is no material difference between the treaties, then the obligation to hold the promised referendum cannot be avoided simply by the fact that it now bears a different name. In my judgment this point is arguable.”

Mr Wheeler remains adamant that his fight will be successful. “The Government made promises which are completely clear and they should not go back on them,” he said.

He rejects the Government's claim that the constitutional treaty was different from the Lisbon treaty.

Speaking at the Law Society in Central London, Mr Wheeler, who has made more than £30million from the spread-betting firm IG Index, said: “If we do have a case, not only do we protect this country's ability to govern itself but we could change the course of European history. The terms of the Lisbon treaty are such that it does not go through unless all 27 member states of the EU ratify it. So if we fail to ratify it there is no Lisbon treaty.”

A spokesman for the Foreign and Commonwealth Office said: “This decision simply means that there will be a hearing — it does not affect the outcome of the case.

“The threshold for what constitutes an arguable case at the permission stage of judicial review is low. Hardline Eurosceptics brought similar cases in respect of earlier European treaties.

“Those challenges all failed. We are confident of the strength of our case on this occasion and look forward to putting our arguments before the court in more detail in due course.”

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