Donald Trump's claim that pockets of London are so radicalised that the police do not dare enter them are "nonsense", Theresa May has said.
The home secretary said Mr Trump's remarks showed he did not understand the UK but she would not be drawn on whether he should be banned for other comments he has made about Muslims.
As home secretary, she has the power to prevent entry on security grounds.
David Cameron has said a Trump visit would "unite" the UK against him.
According to figures published last year, Mrs May has banned more than 217 people since 2010, including 84 hate preachers, 61 people on grounds of national security and 72 because they were deemed "not conducive to the public good".
Mrs May told MPs she would not comment on calls to add Mr Trump - who is leading the polls in the Republican race to be their US presidential candidate - to that list following his own call for all Muslims to be banned from the US in the wake of recent terror attacks in California.
"I think we all agree that the comments Donald Trump made in relation to Muslims were divisive, unhelpful and wrong," she told the Commons home affairs select committee.
"In relation to the question of banning individuals from the UK, given the role I play in making those decisions, I don't comment on individual cases. The decision on whether to ban anyone from the UK is made by the home secretary on the basis of the evidence at the time."
Referring to comments Mr Trump made about parts of London being closed off to the police, Keith Vaz, the Labour chair of the committee, said Mr Trump was "not just any old person from the mid-west of the United States".
"This is the leading Republican candidate for president talking about our country and saying our police are not able to go to certain parts of our country. Do you agree with him?"
Mrs May said Mr Trump was "absolutely wrong" about this.
"I think it was nonsense to say there are parts of the UK where the British police do not feel able to go or not willing to go. I think our police do an an excellent job, day in and day out, working to keep us safe. I just think it shows he does not understand the UK and what happens in the UK."
The home secretary said politicians needed to bring communities together rather than divide them, adding that the Home Office was working with "mainstream voices" in communities to ensure those encouraging hatred did not gain traction.
Earlier, at Prime Minister's Questions, asked by Labour MP Tulip Siddiq whether there was a case for the UK to bar the businessman - who has major commercial interests in the country - the next time he wanted to visit, Mr Cameron replied in Parliament.
"I agree with you it is right that we exclude people when they are going to radicalise or encourage extremism.
"I happen to disagree with you about Donald Trump. I think his remarks are divisive, stupid and wrong and I think if he came to visit our country I think he'd unite us all against him."