A multi-million pound charitable trust is being sued by its former CEO after he claimed he was unfairly dismissed because of his Christian beliefs.

Kenneth Ferguson, CEO of the Robertson Trust from 2011 until this year, is suing for religious discrimination, religious harassment and unfair dismissal.

The Robertson Trust, which issues grants in support of poverty alleviation, is also being sued by the Stirling Free Church, where Ferguson is an elder, over a property dispute.

The church is seeking £10,000 damages for breach of contract and a further £50,000 damages for discrimination after its yearlong contract to rent the trust-owned Barracks conference facility was broken off. 

A notice to quit was served to the congregation despite the agreement permitting the use of the premises "for public worship and delivery of religious instruction".

The church claims this notice came shortly after trust chair Shonaig Macpherson found out about the rental agreement and told senior management that the values of the church were not compatible with those of the trust because of its same-sex marriage beliefs.

Ferguson claims that after this incident, Macpherson started to be rude to him and criticise him in front of other staff members.

He was subject to disciplinary action by the trust over the rental agreement with the church before being dismissed in March this year over "performance issues".

He said: "I was extremely familiar with the trust's funding policy and in particular the trust's policy not to fund any work which promoted religion or was evangelistic in nature. But rental income from hiring out The Barracks was quite obviously not funding.

"The trust had a similar building in Glasgow where for the previous five years had been renting space to many hundreds of charities. There was no policy in place as to who could or could not rent."

Stirling Free Church minister Rev Iain MacAskill said: "We are a thriving church that welcomes all people and preaches the gospel of Jesus Christ. We were shocked to be told we could no longer use the Barracks for our Sunday services.

"We had negotiated with the trust in good faith and their contract expressly refers to us using the premises for religious worship.

"The Free Church believes marriage is between a man and a woman - a mainstream Christian belief shared with the Church of Scotland and the Church of England.

"We had no problems with trust staff during our negotiations. The staff seemed embarrassed when they had to tell us they were terminating our arrangement. We have had no other option but to resort to legal action."

Mr Ferguson and the church are being assisted by The Christian Institute.

Simon Calvert, the Institute's Deputy Director for Public Affairs, said: "Scotland's biggest grant-making trust pride themselves on serving the community. But their actions in relation to Kenneth Ferguson and Stirling Free Church suggest somebody there has a problem with people with orthodox religious beliefs.

"They're trying to claim the rental agreement with the church was against policy when no such policy existed.

"And they've kicked out a much-loved and highly successful CEO while shifting ground on their reasons.

"There's clearly something going on here and we hope these legal actions will bring it to light and secure justice for the Christians who have lost out as a result."

In a statement responding to the allegations, Gerry McLaughlin, Vice Chair of the Roberston Trust Board of Trustees, denied any discrimination had taken place.

"The claim that The Robertson Trust, or members of its board, would discriminate against anyone based on religion or for any other reason, is completely unfounded," he said.

"The Robertson Trust is one of Scotland's oldest and leading funders, supporting charities and communities across the country to help those facing poverty and disadvantage.

"As a member of the Christian faith myself, I am disappointed at the claim that the trust's decision to dismiss the former chief executive was based on religious grounds when in fact the decision was taken based on continued, and documented, underperformance.

"The failure to disclose a conflict of interest when applying trust resources and offering heavily subsidised rates to the Stirling Free Church, of which he is an elder, led to disciplinary action against the then chief executive resulting in a final written warning, but not his dismissal.

"The Robertson Trust's funding policy clearly states that we do not fund projects and activities which involve the promotion of political or religious beliefs.. This has been the case for decades."