The former Belgian prime minister Guy Verhofstadt has announced that he will run for the presidency of the European parliament in a race given added significance by the key role the 751-seat assembly could play in Britain’s departure from the EU.

“In these insecure, turbulent times, when Europe is threatened by nationalists and populists of all kinds, we need visionaries, bridge-builders and compromise-seekers alike,” Verhofstadt said in a video on his Facebook page. “I want to be one of them.”

I am a candidate for the Presidency of the European Parliament https://t.co/OFsdBIkjAP — Guy Verhofstadt (@GuyVerhofstadt) January 6, 2017

Verhofstadt, the Belgian leader of the liberal ALDE group in the parliament, was appointed its lead Brexit negotiator in September. He said he hoped to build “a broad coalition of all pro-European forces that will put the interests of European citizens first”.

MEPs will elect their president on 17 January after the departure of Martin Schulz, who said in November that he was stepping down to return to German politics. The new president will serve until European elections in 2019.

The parliament will play a crucial role in Brexit since it must ratify any divorce agreement between the remaining 27 EU member states and the UK. Theresa May aims to start the two-year exit process by triggering article 50 before the end of March.

A veteran and outspoken European federalist, Verhofstadt warned last month that the parliament could disrupt Britain’s departure unless it was given more than a token role in negotiations. Schulz has also said Britain would do well to take MEPs’ views seriously in talks.

Verhofstadt, who is expected to abandon his role as Brexit negotiator if he is elected president, is up against the Italians Antonio Tajani of the European People’s party (EPP) and Gianni Pittella, from the Progressive Alliance of Socialist and Democrats (S&D).

Under a much-derided agreement by senior MEPs to share the presidency between the two largest parliamentary groups, the role should pass automatically to the EPP candidate after the departure of Schulz, a Social Democrat.

Verhofstadt hopes his candidacy will build a socialist-liberal coalition against the centre right and has positioned himself as the candidate best able to “bridge the gap between right and left … Somebody who can actually win”.

However, the left has rebuffed him, saying it would “exclude any possible under the table deal with the ALDE or any other group”. Pittella said the parliament needed “a real and truly competitive election … This is how democracy works.”

This position may give Tajani the top job. The centre-right candidate can count on the support of his group’s 217 MEPs and should win enough votes from smaller rightwing groups to claim victory.

Without a deal giving him the backing of Verhofstadt’s 68 liberal MEPs, the votes of Pittella’s 189 S&D MEPs are unlikely to be enough for him to be elected.