The European Union has rejected a key Brexit proposal of the British Prime Minister Theresa May, The Sunday Times reported.

According to the source, the situation is complicated as four British ministers opposing Brexit are on the verge of resignation.

The PM hoped to unite her cabinet and overcome the final hurdle in talks with the EU by offering to create an “independent mechanism” to oversee how the UK might leave a temporary customs arrangement if Brexit talks collapsed.

According to the EU, it is possible to monitor compliance with decisions only within the framework of the European Court.

UK  Brexit talks with the EU kicked off in June 2017 in Brussels. Brexit is scheduled to take place on March 29, 2019.