General uncertainty today left markets in Europe down. In the U.K. politicians and the country's treasury issued a stark warning about a possible 'Brexit'. The Treasury said that a vote to leave the European Union could send the country into recession. The vote is now a month away.

In London, the FTSE 100 had a rollercoaster day, closing down 0.32% at 6,136.43. Royal Mail was the biggest gainer on the FTSE, closing 4.3% up after analysts made positive remarks about the mail provider's full-year results. RBC moved their recommendation from underperform to perform.

Satellite operator Inmarsat lost just over 4% today, after disappointing returns issued last week.

In Frankfurt, the Dax closed 0.55% down at 9,861.92 and the Cac 40 closed at 4,325.10, 0.66% down.

Bayer (BAYRY) continued to decline throughout the day, closing almost 6% down, after it unveiled a $62 billion, unsolicited takeover offer for Monsanto MON. The pharmaceuticals and chemicals maker plans to fund part of the purchase with a rights issue.

OCI fell almost 10% in Amsterdam after it was revealed that fertilizers maker CF Industries (CF - Get Report) cancelled a complex $8 billion takeover, after U.S. lawmakers cracked down on tax inversions.

Fiat Chrysler closed more than 4% down in Milan after a German newspaper claimed that the German Federal Motor Vehicle Office had shared suspicions that the car maker had cheated in emissions tests with the European Commission and Italian authorities.

Fiat declined to comment on the Bild-am-Sonntag report but reiterated: "Fiat Chrysler vehicles are in full compliance with current emissions rules."

Greece's ASE index was up 1.5%, closing at 649.10 after the government agreed additional austerity measures. Eurozone finance ministers are meeting tomorrow to assess whether it will unlock the next tranche of its bailout.