BELFAST (Reuters) - Sinn Fein on Monday dismissed as unacceptable a bill proposed by a British Conservative Party lawmaker to set a 10-year limit on prosecuting soldiers, saying it breached a 2014 deal intended to rescue the province’s power-sharing arrangements.

If the bill wins the backing of the British government, it could seriously complicate efforts to resolve a political crisis in Northern Ireland, which is facing a return to direct rule from London for the first time in a decade.

The bill was sponsored by a member of Sinn Fein’s main rival the Democratic Unionist Party (DUP), which did a deal this year to support Prime Minister Theresa May’s government.

Sinn Fein, the largest Irish nationalist party in Northern Ireland, has repeatedly warned that the deal would undermine power-sharing in Northern Ireland.

Conservative Party member of parliament Richard Benyon on Wednesday proposed the bill, which would set a 10 year-statute of limitations “beyond which it would be impossible to bring a case against any individual about whom an allegation was made regarding actions he or she took while serving.”

While presenting the bill, sponsored by DUP lawmaker Emma Little Pengelly, Benyon cited the case of a 78-year-old former British soldier facing prosecution for the shooting of an unarmed 27-year-old Catholic in 1974.

Sinn Fein says the commitment to prosecute crimes committed by British soldiers during the three decade conflict in Northern Ireland is a key foundation of the peace process in the British region.

About 3,600 people died before a 1998 peace deal, approximately half of them killed by Sinn Fein’s former armed wing, the Irish Republican Army. Under the terms of the 1998 peace agreement, Sinn Fein and the DUP have shared power in Northern Ireland for a decade.

The proposed bill is “simply unacceptable,” said Linda Dillon, a Sinn Fein member of the Northern Ireland assembly, who accused British forces of being directly involved in state sponsored killings.

“The decision of the DUP to support it is in direct contravention of the (2014) Stormont House Agreement which ruled out any amnesties and instead provided a range of mechanisms to deal with the past,” she said.

The bill, whose second reading is not due until June next year, was brought to parliament within hours of the collapse of talks between the DUP and Sinn Fein to re-establish a Northern Ireland devolved executive following its collapse in January.

Failure to reach agreement is expected to force the British government to impose direct rule of Northern Ireland, in effect cutting Irish nationalist parties out of the governance of the region during a key stage of Britain’s negotiations to leave the European Union.