Pressure is growing for British Prime Minister Theresa May to reveal how she plans to break the Brexit deadlock as two business giants warn of the dire consequences of a 'no-deal' split with the EU.

Legislators handling Brexit for the European Parliament are urging Mrs May to inform her EU partners how she plans to advance the deadlocked process and reveal what she wants from them.

The EU parliament's Brexit Steering Group said overnight that it "expects the UK side to come back as quickly as possible with a positive and viable proposal on the way forward."

The senior EU lawmakers say the legally-binding withdrawal agreement that would govern Britain's departure cannot be renegotiated, especially the safeguard mechanism to keep the Irish border open.

They insist that "without such an 'all-weather' backstop-insurance, the European Parliament will not give its consent to the withdrawal agreement."

Meanwhile Airbus and Ford have issued stark new warnings about the dire consequences of Britain crashing out of the EU without a deal to protect trade links and supply chains.

Anti Brexit protestor Steve Bray attempts to appear in shot behind a television crew on Abingdon Green, outside the Houses of Parliament, in Westminster, London. (AAP)

Airbus CEO Tom Enders warned of possible factory closures if Britain does not secure a Brexit deal wih the EU. (AP)

Airbus CEO Tom Enders said in a video that a disorderly split would cause Airbus to redirect future investment. The plane maker could not guarantee its existing factories would survive long term.

Ford said that a 'no-deal' Brexit would cost it $AUD1.1 billion in 2019. The estimate reflects the cost of new tariffs and expectations that the British pound would decline in value, a Ford spokesperson said.

And Britain's biggest carmaker will extend its annual production shutdown in April because of Brexit uncertainties, reports the BBC.

Jaguar Land Rover will be idle for an extra week because of fears of disruption at its car and engine plants at Liverpool, Birmingham and Wolverhampton.

Former British Prime Minister Tony Blair. (AAP)

The shutdown during April 8 to April 12 will be in addition to a scheduled closure the following week.

The concerns from the manufacturing giants comes as former British prime minister Tony Blair says the government should hold a second referendum to bring "closure" to the chaotic process.

He believes the chances of such a vote taking place are now greater than 50 per cent.

With just over nine weeks till Britain is due to leave the EU, there is still no deal on the terms and parliament last week crushingly defeated the plan that Mrs May has negotiated.

"I think if you have another referendum it really will bring closure. People like myself accept if the country votes to leave again, that's it," Mr Blair, who opposes leaving the European Union, said.

"But I think if you leave without going back to the people, with this mess and in these circumstances, there will be even greater division."

Mr Blair, who served as prime minister from 1997 to 2007, said Britain could not leave the EU unless it knew where it was heading.

If that meant applying to push back the March 29 Brexit date, then Britain should apply for that, he added.

"The idea that we can tumble out of the European Union without a deal, I mean this would be completely irresponsible and I'm sure that parliament won't allow it," he said.

Meanwhile, an Irish newspaper has claimed that secret plans are being drawn up to deploy Irish police to the border with Northern Ireland in the event of a Brexit deal.

The Irish Independent says about 600 officers could be required to man the estimated 300 border crossings along the 500km frontier, although the chief of the Irish police has denied the report.

"Reports of 600 Gardai (police) to be moved to the border are entirely incorrect. I have not discussed this matter, neither have I considered this proposal," Commissioner Drew Harris said.