A prominent member of UKIP's youth wing has resigned from the party, accusing it of descending into a "form of racist populism".

In a blog on the Guardian website, student Sanya-Jeet Thandi criticised UKIP for running an "anti-immigrant campaign" and of trying to "exploit the ignorance in British society".

She said she would abstain in the forthcoming European elections.

A UKIP source said her resignation was "of no great significance".

The party was growing at a "rate of knots", they added. "She is just one voice out of a total membership of 2,000 in our youth wing."

'Dirty game'

Ms Thandi, a student at the London School of Economics, had been a member of Young Independence, UKIP's Youth Wing, for three years.

She spoke at the 2012 party conference and has appeared on Channel 4 News.

Analysis So why does the resignation of a 21-year-old UKIP member warrant an authored piece in the Guardian and generate national headlines? Would the same happen if a similar figure gave up on the Conservatives, Labour or the Liberal Democrats? To be frank, it probably wouldn't. But UKIP is the new kid at the political disco, with water bombs in his (or her) pockets. Not just that, the party's popularity is rising and so, therefore, is the scrutiny it is under. The single most toxic accusation that can be levelled at the party is racism. Nigel Farage knows that. He held a special event last week, surrounded by supporters from ethnic minorities, to say it was rubbish. Sanya-Jeet Thandi's direct contradiction of this is why her article has grabbed attention.

But, in her blog, she criticised the recent use of a poster saying that 26 million people in Europe were looking for work and asking: "And whose jobs are they after?"

She wrote that "the direction in which the party is going is terrifying: UKIP has descended into a form of racist populism that I cannot bring myself to vote for.

"This week I decided to leave the party and I will abstain from voting in the upcoming European elections. I urge other UKIP supporters to do the same."

She also wrote: "I understand that British politics in the 21st Century has become a dirty game of populism, but UKIP is straying further and further from the policies that attracted so many of its original supporters, instead cynically pursuing ever more aggressive anti-immigrant rhetoric."

UKIP's head of communications, Patrick O'Flynn tweeted that Ms Thandi was going against the trend when it came to Young Independence.

He tweeted: "YI membership topped 2,000 in May, approximately x2 what it was a year ago. Approx 200 new members since start of March."

And a party source told the BBC: "She's a young person and she speaks her opinions. I'm free not to consider them very important.

"I don't regard her as a person I should spend a huge amount of my time bothering about."

The source dismissed her suggestion that UKIP now focussed on immigration above issues like low taxation and a smaller state.

He suggested she was a "theoretical libertarian" and UKIP had a much broader agenda.

Last week, UKIP leader Nigel Farage said the party was "not racist". He told activists that a "handful" of its thousands of candidates had said "stupid or offensive" things, but "they never have, and they never will" represent the views of the party.