Brussels has renewed its threat of legal action against the uk over londons plans to override parts of the brexit deal on northern ireland while vowing to continue contacts in the hope of resolving the dispute.

Maros sefcovic, the eu commissioner in charge of the implementation of last years brexit agreement, told reporters on tuesday that brussels was studying all legal options on the table if the uk failed to back down.

Brussels has set a deadline of the end of this month for the uk to scrap provisions in its internal market bill that would empower ministers to ride roughshod over delicate compromises aimed at preventing a hard border on the island of ireland.

The uk plans, defended by prime minister boris johnson as a safeguard against unreasonable behaviour by brussels, cover key economic issues such as the application of eu state-aid rules in northern ireland and the certification of exports travelling from the region to great britain.

The bill as it currently stands violates the letter and the spirit of the withdrawal agreement, mr sefcovic said, confirming that concessions mr johnson made to his own backbenchers over giving parliament a lock on any future action had not addressed brussels' concerns.

Mr sefcovic and his uk counterpart, cabinet office minister michael gove, announced on tuesday that the joint eu-uk committee charged with implementing last year's deal would meet on september 28 in brussels.

The committees tasks include operationalising the delicate compromise in the treaty that allows eu trade rules to continue to apply in northern ireland while keeping the region formally inside the uks customs territory.

Mr sefcovic urged britain to bring its concerns to the committee table while warning that brussels would not renegotiate the conditions laid out in the treaty.

What we are going to discuss is not the renegotiation of the withdrawal agreement but the timely and proper implementation of the withdrawal agreement, he said.

Mr sefcovic was speaking after a meeting of eu ministers in brussels where france urged the european commission to explore all avenues for countering the uk move, including going to the european court of justice.

The eu-uk brexit treaty empowers brussels to launched infringement proceedings against london for such violations, and also foresees arbitration in the event of disputes.

The eu on tuesday reaffirmed its decision to continue trying to negotiate a deal on a future relationship with the uk despite the dispute over the internal market bill, while warning that ratification of any trade deal would be politically impossible until the spat was resolved.

The stance is in line with the twin-track approach outlined by commission president ursula von der leyen last week of staunchly defending the withdrawal agreement while keeping channels of communication open.

Michel barnier, the eus chief brexit negotiator, told ministers at tuesday's meeting that he would make a final push to secure a trade deal before the realistic deadline of october 31 the date by which the eu has said an agreement must be found if it is to be ratified and applied by the end of the year, when britains post-brexit transition period expires.

We have decided to give one last chance to these negotiations, mr barnier said, according to diplomats present.

Mr barnier is due in london on wednesday for informal talks with uk opposite number david frost. the next full negotiating round is scheduled to take place next week.

Speaking alongside mr sefcovic, germanys eu affairs minister, michael roth, urged britain to knuckle down to hammering out a future-relationship deal.

You have to stop playing around at some stage, he said. we need some serious discussions.