The director for the Coalition for Marriage has handed a petition to Downing Street against plans to change laws to allow gay marriage.
Colin Hart told press outside No 10 that "the government should listen to the people" and to keep existing marriage legislation.
More top news
Freezing cold : wintry, wet & very windy
Farrow will appear on TV on Thursday to discuss the allegation and a claim she makes, saying she wants to "bring down" the filmmaker.
MPs approved the EU (Withdrawal) Bill by 324 votes to 295, at a third reading, with the Government seeing off some proposed amendments.