The First Minister of Northern Ireland is facing questions about his future following the resignation of his son as a junior minister in the province’s Executive.

Ian Paisley Snr, 81, has been drawn into the controversy surrounding his son and namesake’s lobbying on behalf of a property developer.

The DUP leader is facing questions about an office he shares with Ian Paisley Jnr in the constituency they both represent in the Northern Ireland Assembly.

In May 2007 his son caused outrage with homophobic comments he made in a magazine interview.

It also emerged during the recent scandals surrounding MPs employing family members that Mr Paisley Jnr is paid as a ‘researcher’ for his father at Westminster, in addition to his salaries and extensive duties as an Assembly member and minister in the Executive.

Mr Paisley Jnr resigned yesterday as a junior minister in the Office of the First Minister and Deputy First Minister, denying he had done anything wrong.

He is accused of lobbying former Prime Minister Tony Blair on behalf DUP member and property developer Seymour Sweeney’s Giants Causeway development while attending the St Andrews negotiations in 2006.

The talks restored devolved government to Northern Ireland.

Mr Sweeney was bidding to build a visitor’s centre at the Causeway, a unique rock formation.

It is one of Northern Ireland’s best-known tourist attractions and a World Heritage Site.

Mr Paisley Jnr bought a house from Mr Sweeney, despite having claimed that he did not know him but merely “knew of” him.

He claims he paid full market value for the property but has yet to explain why the house is still registered in Mr Sweeney’s wife’s name.

The Times reports:

“He (Paisley Jnr) even got his father to sign an irate letter to the Heritage Lottery Fund complaining that Mr Sweeney’s Giants Causeway proposals had not received grant funding.”

The Paisleys pay £62,500 a year in rent for their Ballymena constituency office, which was originally purchased by a company that Mr Sweeney was a director of.

The office is now owned by Mr Paisley Jnr’s brother in law.

The rent, which amounts to £1,200 a week, is unusually high for an office in a small town in Northern Ireland.

Declan O’Loan, an SDLP assembly member for Antrim North, the same constituency as the Paisleys, said:

“It is clear that within his party the embarrassment has become too great and he had to go.

“The spotlight now switches to Ian Paisley Sr. I think the public will be saying one Paisley has gone, when is the other going to go?”

Gay rights groups and others had been calling on Mr Paisley Jnr to go since May last year, when he gave an interview to a magazine in which he called gay people repulsive and said they harm society.

The Coalition on Sexual Orientation (CoSO), established by lesbian, gay, bisexual and trans groups in the province to provide a voice for the LGBT community, yesterday welcomed his departure.

In September the Northern Ireland Assembly Ombudsman ruled that Mr Paisley Jnr did not break the code of conduct in making his homophobic comments.

His expressions of repulsion for gay people were heavily criticised by partners in the coalition government in Northern Ireland.

Deputy First Minister Martin McGuinness assured the gay community that Paisley Jnr was not speaking on behalf of the devolved administration.

It is widely known that Mr Paisley Snr had become somewhat reliant on his son to assist him with the business of government and many are openly questioning if the octogenarian politician will be able to stay on as First Minister for much longer without Ian Jnr at his side.

Secretary of State for Northern Ireland Shaun Woodward said yesterday:

“On the public front it is obviously a matter for the DUP and obviously a matter for the Executive and Assembly.

“But on a private front I think one also has to acknowledge that, for the Paisley family, it is a very difficult time.

“These matters are always very, very hard and for them, a family who has given a huge amount to Northern Ireland, my thoughts are also with them.”

Ian Paisley Snr’s Democratic Unionist Party is notorious for its extreme hostility to gay equality.

They objected strongly to the introduction of the Sexual Orientation Regulations in Northern Ireland.

The regulations, which became law in the province in January 2007, protect lesbian, gay and bisexual people from discrimination when accessing goods and services.

Lord Morrow, a DUP peer, tried to have them overturned in the House of Lords.

The Lords voted 199 to 68 to retain the regulations.

The result was a defeat for Christian and Muslim protesters, 1,000 of whom converged on Parliament Square while the debate was going on.

Ian Paisley Snr addressed the crowd, asking them, “Are we really Christians and will we stand up for Jesus?

“We’re here to say that we’re on the Lord’s side.”

In the 1970s the First Minister spearheaded a campaign against the decriminalisation of homosexuality in Northern Ireland, “Save Ulster From Sodomy,” and as recently as 2005 he led opposition to civil partnerships

Since taking office in a joint administration with Sinn Fein in May 2007 the DUP has said little about their views on gay rights.