NUS president Aaron Porter apologised today for his "spineless" lack of public support for university occupations around the country.

Speaking at the University College London occupation this morning, Porter said: "For too long the NUS has perhaps been too cautious and too spineless about being committed to supporting student activism. Perhaps I spent too long over the last few days doing the same."

He added: "I just want to apologise for my dithering in the last few days."

Porter had been criticised for not attending the national day of action last week, where school and university students were "kettled" in Whitehall for several hours by police, and for taking several days to issue public support for university occupations which sprung up in protest against the rise in tuition fees and the scrapping of education maintenance allowances.

Porter was speaking at UCL following tweets from the university's occupiers last night which called for a vote of no confidence in Porter's presidency. At a meeting with the protesters in the university's Jeremy Bentham room, Porter said he wanted to avoid a civil war within the student movement.

He said: "I want to be clear and unambiguous right now. Wherever there is non-violent student action, NUS should and will support that. What we are facing is utterly disgraceful and for us to engage in some kind of internal civil war is exactly what our opponents would want."

He also agreed to support a list of demands made by the UCL occupation. He said that NUS would:

• Publicly support all student occupations on the frontpage of the NUS website and all available media.

• Call immediately for a new wave of occupations as a legitimate form of protest against fees and cuts.

• Organise financial, legal and political aid for all current and future occupations.

• Call a national day of action on the day of the parliamentary vote on tuition fees.

• Officially support any staff taking further industrial action on cuts.

He also said he supported the next nationwide "day of action" on Tuesday.

Speaking to the Guardian after his speech, Porter denied the NUS had lost the leadership of the student movement, which has grown independent of the union in recent weeks.

"I genuinely believe that the NUS has been more uniting than it has been since I was [first] involved. I hope that my style of presidency allows different types of action to be supported under a bigger student movement.

"I can't please every student all of the time, but I think I'm doing more than we've done previously."

Porter also said he wished he had been at the protests on Wednesday, but said he had been absent for valid reasons – he was meeting trade union leaders.

"I would have liked to have been but I think it was more important for me to meet lots of other trade union leaders, to make sure this movement isn't just a student movement."

He also strongly condemned the treatment of the kettled protesters that day, but refused to apologise for the language he used to criticise those who stormed Milbank on 10 November.

He said: "I stand by calling acts of violence 'despicable'. I think it is and I think it does undermine our cause.

"I'm much more interested in talking about the majority of students who came out to make a serious and important point and they did so in a tremendous way. I'm incredibly proud of those students.

"If it had been a non-violent direct action, yes I would have supported it. And unfortunately that's not what happened, and certainly not what the public think happened."