According to the TUC, almost half (46.2%) of employees earn more than £350 a week so this level of redundancy pay means many will miss out. The union advises the rate should be increased to £500.
The TUC is also lobbying for the amount people receive in redundancy pay before tax to be increased from £30,000 to £50,000.
Brendan Barber, TUC general secretary, said: "There can be no assumption people who are losing their jobs will get new ones and they will need all the help they can get with redundancy pay."
But Katja Hall, director of employment policy at the Confederation of British Industry (CBI), believes this will put unnecessary pressure on already struggling employers.
She added: "The TUC's call for increased redundancy and tax-free lump sum payments is understandable but raising the weekly rate for redundancy payments will put even more jobs at risk by increasing the financial pressure on distressed businesses at a critical time.
"Employers do not take the decision to lay off staff lightly. The emergence of many different short-term working patterns is evidence of that. The focus must me on keeping business working and as many people as possible in jobs."
Statutory redundancy pay should be based on GBP500 weekly average earnings, says TUC
The amount of weekly earnings, which counts towards statutory redundancy pay, has risen from 330 to 350 but, according to the TUC, in real terms, this is less than the original value of redundancy pay when it was introduced in 1965.
