Andy Bathie, 37, initially agreed to help Sharon and Terri Arnold after being assured he would not have to be involved in the upbringing of their young boy and girl or have any financial responsibility towards them.
But the British government's Child Support Agency has begun docking his pay to force him to contribute to the children's upbringing because the lesbian couple have split up.
Mr Bathie has launched unprecedented court action in an attempt to ensure he cannot be recognised as a legal parent to the children.
"These women wanted to be parents and take on all the responsibilities that brings," he told the Evening Standard newspaper.
"I would never have agreed to this unless they had been living as a committed family.
"And now I can't afford to have children with my own wife - it's crippling me financially."