A party panel decided to expel Atkinson after a member of her staff was filmed apparently asking for an inflated restaurant invoice to claim on EU expenses.
"Janice Atkinson MEP and Christine Hewitt (assistant to Janice Atkinson) have been found to have brought the party into disrepute," a spokesman said yesterday.
"As a result they have been expelled from UK Independence Party. They have 14 days to appeal."
Police are investigating the alleged fraud, which UKIP leader Nigel Farage had described as appearing to be "one of the most incredibly stupid and dishonest things I've ever seen in my life".
Also Read
In a statement, Atkinson said she intended to appeal against the decision.
"I am deeply disappointed by today's decision and fully intend to appeal," Atkinson's statement said.
"I was elected to represent the constituents of the south-east of England and I will continue to work tirelessly on their behalf and for the best interests of our country."
UKIP had surged in support from being a fringe movement to claiming the largest vote share of any party in the European Parliamentary elections in 2014.
UKIP argues that immigration can only be controlled if Britain leave the European Union, and demands a sooner referendum than a vote promised by Cameron for 2017 if he is re-elected.
UKIP candidates have been involved in a series of blunders, and Atkinson herself had previously hit headlines for describing a Thai member of UKIP as a "ting tong".