Jill Seymour and Margot Parker, who represent Midlands constituencies, both also heavily criticised Gerard Batten, the current UKIP leader.
Seymour said she was “proud” to have helped UKIP “grow from strength to strength under the leadership of Farage, leading up to its success at the 2014 European elections.”
But she said that UKIP, under Batten, had “abandoned its centre ground and chosen to instead occupy the extreme right of politics.”
“I am not walking away from the party’s original core principles, but the present party’s direction means it has walked away from me, and its original membership,” she said.
“I shall now be sitting as an officially-designated Brexit Party MEP for the remainder of my mandate in the European Parliament.”
She added: “It is a disgrace that we are even in a position to be talking about having European elections once again, but I would ask everyone who believes in democracy, and honouring the result of the 2016 referendum, to show the political establishment they are disgusted with the betrayal of Brexit by the UK government, and go out and vote, believing in Great Britain and its independence.”
Under Farage’s leadership, UKIP, she said, had “gained brand recognition, and an army of stalwart supporters.”
“I am not walking away from the [UKIP] party’s original core principles, but the present party’s direction means it has walked away from me, and its original membership” Jill Seymour MEP
“It was the hard work of the grassroots membership who helped me, and my colleagues, to persuade the British public to vote overwhelmingly for UKIP in the 2014 European elections.”
“No one person should ever be bigger than a political party, but sadly I believe that Batten will be instrumental in its demise.”
She accused Batten of attempting to ‘bully’ her into leaving the EFDD ‘Brexit Group’ in the European Parliament and follow him into a rival far-right affiliation.
“It was suggested that, if I did not do this, it would be a black mark against me. I do not appreciate being bullied by what is clearly just an attempted points-scoring exercise against Farage and his new Brexit Party.”
She added, “I still see genuine people in UKIP who believe in my values and will give their last breath to protect those values. But UKIP officials have left a bitter taste in the mouths of many loyal and dedicated past and present members, who now seek a new type of party.”
“It is the Brexit Party that will return our country from the EU and deliver true democracy,” she said
Her husband Brian, a UKIP donor for more than 20 years, has also resigned from his lifetime membership of the party.
"The policies of the leader have now so damaged the party, I feel I must resign my position and membership of UKIP. This I do with great reluctance and sadness in equal measure” Margot Parker MEP
Elsewhere, Parker, who was UKIP spokesman on women's rights and gender equality, said: "The party leader of UKIP is carrying out a purge of party loyalists to ensure only supporters of the far-right activist Tommy Robinson, with whom he now associates, are considered for approval by the party.”
"The policies of the leader have now so damaged the party, I feel I must resign my position and membership of UKIP. This I do with great reluctance and sadness in equal measure.
"The leader seems to be engaging on a 'crusade' on issues, which are dividing communities up and down the land.”
"He has taken his eye off the ball - the goal has to be Brexit and that is why I have joined the new Brexit Party, which aims to change the political landscape and fight for what people voted for in the 2016 referendum.”
"Furthermore, the leader of UKIP has deselected hard-working, sitting, female MEPs. I have fought long and hard for equality - I cannot be part of this distasteful regime any longer."
Parker said she will see out the rest of her mandate.
On Tuesday, no-one from UKIP was immediately available for comment. It is believed that both UKIP and the Brexit party will field candidates in May’s European elections.