Jill Seymour MEP has resigned her position as UKIP Transport spokesman, with immediate effect.
The West Midlands MEP has held the post since being elected to the European Parliament in 2014, but says she is ‘struggling to be loyal to a party that is changing direction’.
Mrs Seymour has written to UKIP leader Gerard Batten, and to the party’s NEC, to inform them of her decision, saying: “I joined UKIP 18 years ago to fight for our country’s independence and its self-determination; being good neighbours with our European friends, without being suffocated by EU laws.
“However, over the past few months the party has moved away from our core beliefs – the main one focusing on the betrayal of Mrs May and her EU friends, who have quietly deceived the 17.4 million leave voters.
“We should have been the most prominent Brexit party, holding meetings and campaigns across the UK over the past months, leading up to 11th December and beyond until March 29th. Sadly, I do not believe this has happened.”
She said Mr Batten’s decision to stand by controversial figures was causing unrest, not just within the party, but across the country.
And she added in her letter: “Many of our colleagues and loyal activists are resigning from the party because of your decisions, and this is very concerning.
“I am struggling to be loyal to a party that is changing in direction, and conscious of the grassroots who look upon us for support.
“I have begged you to listen and be guided by the NEC and your friends, which you have the right to ignore, but feel this could be at the cost of both yourself, and the party.
“You have made it difficult for me, and many, to stay true to the party and our leader, so I feel I have no alternative but to resign from your front bench team, and consider my future.
“I appeal to you to reconsider your present direction; to focus purely on fighting the establishment who are clearly betraying millions of us that wish to leave the EU. This is the only subject this country should be discussing right now.”