Theresa May is facing calls from the European Parliament’s Brexit chief to condemn Poland’s autocratic government as a “test” of the UK’s commitment to the EU’s liberal, democratic values and the future relationship with Europe.

The demand came as the European Commission meets on Wednesday to discuss whether to launch unprecedented “Article 7” legal proceedings against Poland's hardline conservative government for violating the EU’s commitment to democracy and human rights.

The threat to make Poland a pariah in the EU family comes at a highly embarrassing moment for Mrs May who is due to visit Warsaw on Thursday as part of a massive diplomatic charm offensive that has been launched by Britain towards Poland since Brexit.

Guy Verhofstadt, the head of the European Parliament’s Brexit working group, told The Telegraph that Mrs May’s visit to Warsaw would provide a clear “test” of where the UK’s true loyalties now lie.

"The current Polish government is guilty of backsliding on the rule of law and undermining European democratic values,” he said.