UKIP employment spokeswoman Jane Collins MEP has called Ford "hypocrites" for encouraging workers to vote to remain in the EU by threatening job uncertainty, saying "what we do know for certain is that Ford used our money to relocate British jobs to Turkey."
In a quote published by the 'stronger in' campaign on twitter, the letter sent to 14000 workers said they have "deep concerns about...the potential downsides" of Brexit.
But Mrs Collins said the "downsides" for Ford and other big companies would be that they would find it "less easy to take British tax payers money to export jobs."
"At the same time these workers have to rely on the Treasury to top up their meagre salary with benefits so we subsidise these companies once again.
"Ford have taken loans at a very low interest rate from the EIB of which the UK is the second biggest contributor to open and expand their plant in Turkey.
"The cost of this has been job losses in Southampton and soon in Dagenham - the home of the UK's fight for equal pay in Britain.
"Even today the European Commission responded to a question I asked about wages in the UK post Brexit and refused to endorse the ludicrous and economically illiterate claims that wages would fall should we take control of our country.
"Big companies love the EU - it keeps them rich and their workers poorer"