Image copyright Press Eye Image caption Ciaran McClean stood unsuccessfully for the Green Party in West Tyrone in the general election

A legal challenge against the deal between the Democratic Unionist Party and the Conservatives has failed at the High Court in London.

The DUP agreed to support Theresa May's government in return for £1bn for Northern Ireland over five years.

Ciaran McClean, a Green Party member, argued the pact breached the Anti Bribery Act 2010.

Lord Justice Sales said the grounds relied on by Mr McClean were not "properly arguable in a court of law".

Mr McClean launched a crowdfunding campaign to finance the case, which he brought independently of political parties, in July.

Lord Justice Sales and Mr Justice Lewis heard the application for a judicial review on Thursday.

Dominic Chambers QC, acting for Mr McClean, told the court the confidence and supply agreement was unlawful as it "purchased" the political support of the DUP.

He said it was "unlawful because it makes provision for the expenditure of public funds for party political advantage".

The application was contested by both the First Secretary of State, Damian Green, and the Attorney General.

Image copyright Reuters Image caption Under the deal, the DUP guarantees its 10 MPs will back the government on legislation relating to Brexit and national security

In a written submission to the court, James Eadie QC for the government argued that the criminal law of bribery does not apply to a confidence and supply agreement between political parties.

"The allegation that the agreement entails public expenditure which is unlawful is misconceived because the expenditure contemplated by the agreement will have appropriate parliamentary authorisation," he wrote.

After the verdict, Mr McClean told the BBC that he is considering an appeal.

"We put the most serious charges to any government in modern times and the consequences of that could have been the fall of the government and the government finding themselves in the dock," he said.

"I don't think that was ever going to happen. But I think it was still right to get this aired."

His solicitor, David Greene, is a senior partner at London-based Edwin Coe solicitors, who represented hairdresser Deir Tozetti Dos Santos, one of the claimants in the successful Brexit challenge in the Supreme Court.

Following the judgement, lawyers representing the government were awarded full costs.

Lord Justice Scales said it was "not appropriate for the burden of costs to be borne by the taxpayer".

Under the confidence and supply arrangement, the DUP guarantees that its 10 MPs will vote with the government on the Queen's Speech, the Budget, and legislation relating to Brexit and national security - while Northern Ireland will receive an extra £1bn over the next two years.

Image copyright Getty Images Image caption The Tory-DUP deal came two weeks after June's election resulted in a hung Parliament

While rival parties in Northern Ireland have largely welcomed the additional funding, concerns have been raised that the deal could undermine the peace process and devolution negotiations, with the UK government dependent on the support of the DUP.

The deal was also widely criticised by opposition parties in the UK.

Labour branded it "shabby and reckless", while the Welsh First Minister Carwyn Jones called it a "straight bung" and said it "kills the idea of fair funding".