Britain's Prime Minister Theresa May leaves 10 in Downing Street in London, Britain, November 28, 2018. REUTERS/Henry Nicholls

LONDON (Reuters) - Britain’s government intensified its warnings about a no-deal Brexit, saying it would deliver a big blow to the economy while Prime Minister Theresa May’s plan, opposed by many lawmakers, would minimize the hit.

The government said that in a scenario based on the agreement May struck with other European Union leaders on Sunday, the economy would be 2.1 percent smaller in 15 years’ time than if the country remained in the bloc.

The forecast assumed no changes to migration rules but some non-tariff barriers.

The economy would be 7.7 percent smaller if there is no deal, the government said in a report published on Wednesday.