Eminent parliamentarians have lost a Supreme Court battle over Home Secretary Theresa May's decision to ban a dissident Iranian politician from Britain.

An appeal by the cross-party group of 15 MPs and peers, led by Liberal Democrat Lord Carlile, was rejected in a majority ruling by justices at the UK's highest court today.

They had previously lost actions in the High Court and Court of Appeal over the exclusion of Maryam Rajavi.

The politicians wished to invite Mrs Rajavi, who is now living in Paris, and is recognised internationally as an expert on Iranian political affairs and the position of women in Islam, to address meetings to be held in the Palace of Westminster to discuss ''democracy, human rights and other policy issues relating to Iran''.

Their complaint related to the "interference with their rights" in relation to freedom of expression, caused by exclusion decisions by the Secretary of State.

Mrs Rajavi, who has been excluded from the United Kingdom since 1997, also unsuccessfully appealed alongside the parliamentarians against decisions made by the Home Secretary to maintain her exclusion.

The Home Secretary stated that lifting the exclusion would cause significant damage to the UK's interests in relation to Iran and place British people and property in Iran and the region at risk.

Both the High Court and Court of Appeal held that the exclusion was "justified and proportionate".

The Supreme Court dismissed the appeal by a majority of 4-1.

Lord Sumption, who dismissed the appeal, said the UK "has had a uniquely difficult relationship with Iran for at least a century and a half".

He said: "The passage of time heals many things, but in an ancient and distinctive national culture like Iran's, injured pride can subsist for generations.

"In recent years, the participation of the United Kingdom in international sanctions against Iran and a number of violent incidents have revived old suspicions at a time when negotiations with Iran about middle eastern issues, nuclear non-proliferation and human rights have assumed considerable importance for British interests and global security."

It was against this background that the Home Secretary, on the advice of the Foreign Office, decided that it was not conducive to the public good to allow Mrs Rajavi to enter the UK.

Mrs Rajavi, who has close links with Iranian opposition organisations, is not excluded from any other European country and engages regularly with parliamentarians in the European Parliament.

The bid to lift the ban on her entering the UK began in 2010. Dismissing the latest challenge, Lord Sumption said that "on the undisputed facts before the Secretary of State it has not been shown that she was guilty of any error of principle".

Lord Neuberger, president of the Supreme Court, said: "I consider that it is not open to a court on the facts of this case to conclude that the decision of the Home Secretary to refuse entry to Mrs Rajavi was unlawful."