However, public sector union Unison, which has been campaigning for the nurseries, said the fight was not over yet.
The settings at Marylebone and Harrow had been due to close in September but were granted a temporary reprieve to give time for Unison and the nurseries' staff to draw up a business plan with a consultant.
This was presented to senior management on 30 October. But the university concluded that the plan was not viable, and on Monday it was announced that the nurseries would close on 31 December.
Eight nursery staff stand to lose their jobs and 40 children will be forced to find other childcare facilities.
Westminster university registrar and secretary Carole Mainstone said, 'This is a challenging time financially. We must conclude with deep regret that we cannot afford to run our nurseries – particularly as the number of students using the service is so low.'
The nurseries have a list of more than 30 student parents who wanted to use the facility this term, but the university has stopped new parents from registering.
The business plan submitted had included a proposal to raise the nursery's fees by 20 to 25 per cent, which the union argued would have kept them competitive and affordable for students. Fees are currently from around £89 a week.
Unison branch secretary Barry Blinko said the union was appealing against the decision and would take the case to the university's Court of Governors at a meeting later this month.
He said that the decision to close the nurseries threatened student retention, because many student parents could be forced to abandon their studies if the nurseries closed.
Mr Blinko said, 'Closing these two nurseries will only save about £120,000 per year, but will cost student parents their education. At the same time, the college is planning to spend £1m on a new reception area. Where is the sense in that?
'Our equality impact assessment showed that these cuts are set to hit women hardest. It is vital that the college rethink its plans.'
A petition to save the nurseries has been signed by nearly a thousand people.
Christina McAnea, head of education at Unison, said, 'Many universities and colleges see nurseries as soft targets for cuts. But this is totally unacceptable. These nurseries are often the only affordable childcare options for students with young children. The closures will price many parents, especially women, out of continuing their education.'
She added, 'Unison is deeply worried about this growing trend and are campaigning hard against the cuts. The government has worked hard to get more students from different backgrounds into university. By excluding students with children, these cuts threaten to turn back the clock to the bad old days when only the privileged few could continue their education.'