By Pietro Lombardi

VALLADOLID, Spain (Reuters) - European Union climate chief Frans Timmermans did not rule out a potential return to Dutch politics on Tuesday, following the collapse of Prime Minister Mark Rutte's conservative government.

Timmermans, a socialist politician and member of the Dutch Labour Party, has previously served as Dutch foreign minister. He is being touted in some quarters as a potential prime ministerial candidate if he can garner sufficient support before an election expected in November.

The Labour Party and the Green Party are holding a referendum to decide whether to present a joint programme, he told journalists at an informal meeting of environment and energy ministers in Valladolid, northwest of Spain.

"Anything I would say now would disturb that process," he said when asked about his interest in returning to Dutch politics.

"It is up to members of both parties to express themselves and then everybody will have to make up their minds," he continued.

(Reporting by Pietro Lombardi; Editing by Aislinn Laing and Emma Rumney)