The Democratic Unionist Party will vote against Rishi Sunak's deal on trade rules in Northern Ireland, the party's leader announced Monday in a blow to U.K. government efforts to restore power sharing in the region.

In a statement released ahead of the Windsor Framework deal's first parliamentary vote Wednesday, Jeffrey Donaldson said his party will oppose it due to their "ongoing concerns."

"It is our party view that there remain key areas of concern which require further clarification, re-working and change as well as seeing further legal text," Donaldson said, following a meeting of his party's top brass.

Sunak secured the EU-U.K. deal February after months of negotiations over contentious post-Brexit trading rules in Northern Ireland.

The British prime minister was keen to secure the blessing of the DUP, which walked out of the region's power-sharing institutions last year in protest at the protocol — which kept Northern Ireland bound to EU standards on goods.

The first vote Wednesday is on the so-called "Stormont brake" element of the deal, which gives the currently-defunct Northern Irish Assembly the power to veto any new EU regulations from applying in the region provided parties agree to re-establish the power-sharing administration.

Donaldson said this "does not deal with the fundamental issue, which is the imposition of EU law by the protocol."

The DUP's move came shortly before the U.K. government unveiled the legislation MPs will vote on Wednesday.

A new statutory instrument — a form of secondary legislation under U.K. parliamentary rules — sets out the 'Stormont brake' and will now be pored over too by Conservative MPs in the European Research Group of Brexiteers ahead of their verdict, expected Tuesday.