The EU has launched four new legal cases against the UK government in response to MPs' support for legislation overriding post-Brexit arrangements for Northern Ireland.

The claims concern previous failures to implement the 2019 deal agreed with Boris Johnson, but the EU has been prompted to act by the passage of a bill through parliament that would rip up current arrangements.

The Northern Ireland protocol bill passed its third reading in the House of Commons on Wednesday by a vote of 267 to 195, and will now go to the House of Lords in the autumn.

The four new legal cases, which allege a failure to enforce EU customs, VAT, and excise rules, join three other cases already pending before the European Court of Justice.

It is worth noting that the EU court has the authority to levy daily fines of millions of euros on the UK, and its decisions could be the first step toward the bloc taking punitive action through mechanisms built into the Brexit agreements.

On his account, the EU's Brexit commissioner Maros Sefcovic has not ruled out tariffs on British goods sold into the EU, calling the terms of the Northern Ireland protocol bill "illegal."

The commission said in a statement on Friday that it was taking the legal action in part because of "the continued passage of the Northern Ireland protocol bill through the UK parliament," which it said "goes directly against" a spirit of seeking joint solutions to current issues.

Under Johnson's 2019 protocol, Northern Ireland effectively remains in the single market, with EU customs rules applied down the Irish Sea to elude a border on the island of Ireland. 

Read more: Sinn Fein leader says N. Ireland being sacrificed in Tory "games"

The proposed legislation would eliminate checks for firms selling goods from the United Kingdom to Northern Ireland rather than the EU.

The UK government envisions a "green lane" with fewer checks for those selling goods to Northern Ireland and a "red lane" with existing checks for goods destined for EU countries.

According to EU officials, there are no significant differences between this proposal and those put forward by the European Commission for an "express lane."

However, the legislation would also allow companies in the United Kingdom exporting to Northern Ireland to choose between meeting EU or UK regulatory standards, which are expected to diverge increasingly. 

According to EU officials, this poses a risk to the single market and that the current arrangements and failure to implement controls have already encouraged smugglers.

Other measures include shifting trade dispute resolution away from the European Court of Justice and toward independent arbitration.

The UK foreign secretary Liz Truss, who drafted the legislation, is the frontrunner to become the Conservative Party's next leader and Prime Minister following Boris Johnson's resignation. 

She has pushed for the Northern Ireland protocol bill as proof that she makes "tough decisions."

Read more: PM Johnson using N.Ireland against EU: Sinn Fein leader