Sadiq Khan, the Labour candidate for London mayor, has said there is “a question to be asked” about why some Muslim women in the capital wear hijabs and niqabs.

Khan, who became the first Muslim cabinet minister in Gordon Brown’s government in 2009, warned of an “insidious” development if people thought it was right to treat women differently to men.

In an interview with the London Evening Standard, the frontrunner in next month’s mayoral contest contrasted the way Muslim women dressed when he was growing up in London in the 1970s and 80s with the way many women dressed today.

Khan, 45, said: “When I was younger you didn’t see people in hijabs and niqabs, not even in Pakistan when I visited my family. In London we got on. People dressed the same. What you see now are people born and raised here who are choosing to wear the jilbab [a loose gown] or niqab.

“There is a question to be asked about what is going on in those homes. What’s insidious is if people are starting to think it is appropriate to treat women differently or that it has been forced on them. What worries me is children being forced to adopt a lifestyle.”

Khan suggested Muslim women should think about whether to wear the niqab, which covers the face, when they interacted with providers of public services. Asked whether women should be allowed to cover their faces, he said: “It’s not for me to tell women what to wear. But I do think that in public service we should be able to see each other’s faces. Eye contact matters. You should be able to see the face.”

He added: “There is no other city in the world where I would want to raise my daughters than London. They have rights, they have protection, the right to wear what they like, think what they like, to meet who they like, to study what they like, more than they would in any other country.”

During the interview Khan sought to answer critics who say that his record as a human rights lawyer means he would be soft on terrorism.

Zac Goldsmith, Khan’s Tory opponent, has been criticised after his campaign distributed leaflets describing the Labour candidate as “radical and divisive”. Khan tweeted this week: “Hey @ZacGoldsmith. There’s no need to keep pointing at me & shouting ‘he’s a Muslim’. I put it on my own leaflets.”

Khan said he would never apologise for his work as a human rights lawyer. But he pledged to place London on a “war footing” to tackle terrorist threats. “On day one I am going to put us on a war footing with these terrorists,” he said. “That will mean having a major review of our capabilities to deal with this.”

Khan said he was the best-qualified candidate to deal with terrorism because he was the only one with security clearance as a privy councillor. “Do you think I’d have been invited to weekly security meetings where there were MI5 and MI6, representatives from the police service and chaired by the home secretary if there were any concerns about me?”

He said he had been singled out by extremists – and been given police advice on protection – because of his liberal views, particularly on same-sex marriage. “There are people in Tooting who no longer talk to me because of it. When I was first elected I had all sorts of problems from these extremists. There was a fatwa put out against me. I’m the person with the plan in relation to fighting extremism.”

Goldsmith told the Evening Standard this week that Khan had been “giving platform, oxygen and cover” to extremists, and highlighted Khan’s decision to share a platform with Suliman Gani, an imam whom he described as “repellent”. His attack backfired when it emerged that Goldsmith had posed for a photo with Gani.