U.K. Prime Minister Boris Johnson will send his Brexit law-breaking proposals to Parliament this week, facing a growing rebellion from his MPs and further criticism from former premiers and European Union leaders.

Johnson’s plan, which would allow the U.K. to unilaterally override parts of the divorce treaty it signed with the EU, will be debated and voted upon as part of the government’s internal-market bill in the House of Commons on Monday. The EU has threatened legal action unless Johnson backs down by the end of the month, a request his government has rejected.

The risk for Britain is that the controversy around Johnson’s plan increases the prospect of ending the Brexit transition period without a free-trade accord with the EU, causing an economic shock as tariffs and quotas are introduced on commerce with its biggest trading partner.