Academics' unions have called for an inquiry into the pay of university vice-chancellors after a survey showed 18 earn at least £200,000 a year.
Natfhe and AUT members went on strike on Tuesday
The AUT and Natfhe unions, representing lecturers and academic staff, called for scrutiny following the survey by the Times Higher Education Supplement.
The AUT have asked why vice-chancellors deserve such high salaries.
But Universities UK said such packages are needed to attract and retain staff in a competitive market.
The survey found more than 30 vice-chancellors can claim higher salaries than the £169,000 earned by Prime Minister Tony Blair, and that pay for university bosses increased on average by 25% between 2001-02 and 2004-05.
Members of the AUT and Natfhe went on a national one-day strike over pay on Tuesday, and a boycott of assessments and appraisals has begun.
Sally Hunt, general secretary of the AUT said: "I think there is a real and urgent need for vice-chancellors' pay to be properly scrutinised and all rises to be conducted in a transparent manner.
She added the union would be calling on the education secretary for a proper investigation into why vice-chancellors are paid so highly.
Roger Kline, head of the universities department of Natfhe, also supported an inquiry.
He said lecturers would settle for the 25% pay rise vice-chancellors had awarded themselves, but pointed out an independent inquiry into lecturers pay had supported their case for significant salary increases.
But Universities UK, which represents vice-chancellors, and university employers' group Ucea said vice-chancellors' pay was justified in an increasingly competitive global market .
"Vice-chancellors do a demanding job as chief executives of complex, multi-million-pound organisations," they said in a joint statement.
"Their remuneration packages reflect what it takes to attract, retain and reward individuals of sufficient calibre, experience and talent in a growing sector.
"The average percentage increase in vice-chancellors' pay for 2004-05 was well below the average for chief executives in both the public and private sectors," they added.