Sinn Féin's five elected MPs have claimed over £100,000 in London living allowances last year, despite refusing to take their seats at Westminster.
Gerry Adams, Martin McGuinness, Michelle Gildernew, Conor Murphy and Pat Doherty claimed £21,000 each in parliamentary expenses for second homes in London.
But the party members do not sit in the Commons because they refuse to swear an oath of allegiance to the Queen.
A Sinn Féin party spokesman said: "We were given the same allowances that other parties are entitled to. We rent two houses in London. We publish an audit of our expenses every year in Dublin."
But shadow Northern Ireland secretary Owen Paterson told The Daily Mail that it was "unacceptable" that the representatives claimed a London allowance.
He stated: "It is completely unacceptable for Sinn Fein representatives, who won't even sit in Parliament, to claim hundreds of thousands at the taxpayers' expense. That is why the Conservatives have consistently opposed members who refuse to take their seats receiving the accommodation allowance."
Tom Elliott, an Ulster Unionist Member of the Northern Ireland Assembly, added: "It is time for Sinn Féin to stop being so hypocritical."
"They sit under the Crown in the Assembly, a devolved institution within the United Kingdom.
"In that assembly they pass legislation which is ratified by the Queen. Some may ask what the difference is."
A Sinn Féin party spokesman later said: "Sinn Féin MPs do not receive a salary from Westminster. Sinn Féin makes no apology for refusing to sit in the British House of Commons."
