Boris Johnson's controversial Brexit legislation which allows the Government to break international law has been backed by MPs.

The Internal Market Bill tonight cleared its final stage in the House of Commons by 340 votes to 256 and now passes to the Lords for further scrutiny.

It allows ministers to override parts of the Brexit Withdrawal Agreement brokered with Brussels last year, an act which the Government concedes breaches international law 'in a limited and specific way'.

Critics, including all five living former prime ministers, also argue this would wreck the UK's reputation as a nation which honours its agreements.

But the Government insists it needs the powers to safeguard the integrity of the UK amid fears the EU could block goods travelling between Great Britain and Northern Ireland.

The Prime Minister was forced to water down the legislation earlier in the Bill's passage to appease a Tory backbench rebellion - MPs will now be given a vote before ministers are able to wield such powers.

No Conservative MP voted against the Government tonight and the Bill sailed through the Commons with an 84-vote majority.

Yet a handful of Tories, including former Tory prime minister Theresa May, abstained from voting.

However the Bill's smooth passage into law will likely face hurdles in the pro-Remain Lords which has previously thwarted Brexit legislation.

Defending the controversial aspects of the Bill at its third reading tonight, Business Secretary Alok Sharma said: 'The reason we have taken powers to ensure that in the event we do not reach an agreement with our EU friends on how to implement the (Northern Ireland Protocol) is so we're able to deliver on our promises in our manifesto and the command paper.

'This is a legal safety net that clarifies our position on the Northern Ireland Protocol for protecting our union, businesses and jobs.'

To avoid checks on goods passing between Northern Ireland and the Republic of Ireland, the UK and Brussels agreed Northern Ireland would abide by the EU's customs rules.

It in effect draws a customs border down the Irish Sea, and ministers fear unfettered movement of goods between Great Britain and Northern could be compromised if a deal is not reached.

The EU has warned it will mount a legal challenge if the UK reneges on sections of the Withdrawal Agreement.

Shadow business secretary Ed Miliband tonight said: 'On international law, nobody should be in any doubt the damage already done by this Bill. This law-breaking Bill has been noticed around the world.'

He pointed to reservations made by Donald Trump's Northern Ireland envoy Mick Mulaney: 'When the Trump administration starts expressing concern about your adherence to international agreements and the rule of law, you know you are in trouble.'

The Bill also contains powers which enable Westminster to provide financial assistance for economic development, infrastructure, cultural activities and education purposes across the country.

Opposition MPs have warned it will give the UK Government the chance to stray into matters which are devolved in Scotland, Wales and Northern Ireland, branding it an 'attack' on devolution.

SNP MP Mhairi Black said: 'This Bill explicitly gives any minister of the Crown permission to run riot with the very assets of Scotland that our Scottish Parliament has protected.'

Independence, she said, 'is the only option left for Scotland', adding: 'This is a union that England dominates. The only reason there isn't an English Parliament is because the people in Westminster view this place as the English Parliament, and we can't afford to be naive. The only way to protect our Parliament is to become independent.'

She added: 'It took us 300 years to get our Scottish Parliament and 20 years for this place to put a bulldozer right through it.'

Mr Miliband told the Commons: 'On devolution, we on this side believe deeply in our Union but the strength of our Union relies on sharing power not centralising it, and this Bill does not learn that lesson.

'It makes the choice to impose the rule that the lowest regulatory standard in one Parliament must be the standard for all without a proper voice for the devolved administrations.'

Mr Miliband said he fears the Bill will 'strengthen the hand of those who want to break up the UK'.

The Bill will undergo further scrutiny in the Lords at a later date.