But the plan could come to nothing because of a split in the credit union movement, with another representative body, the National Federation of Credit Unions, strongly opposed to changing existing rules.
Credit unions are self-help organisations that bring together people with common interests. They save within the union and borrow at cheap rates.
Borrowings may not be charged at more than 1 per cent per month, an annual percentage rate of 12.68 per cent. A dividend is paid on savings, typically about 4 per cent per year. Deposits are limited to pounds 5,000, and borrowings to the value of the depositor's savings plus pounds 5,000.
Abcul says the savings and borrowing limits are now out of date.
One of the most recently established unions, and the first promoted within a large public company, is at British Airways. Pilots have already indicated that they would like to save more than the limit.
Stephen Bellaby, spokesman for the NFCU, said: 'These proposals could be seen as beneficial, but that is over-ridden for us by concerns that credit unions occupy a particular niche and philosophy of co-operation and self- help. They could become just another financial institution.'
The NFCU has about 200 union members and 67,000 individuals, and Abcul has about 250 unions affiliated, with about 80,000 individuals.
A report published this month by the Joseph Rowntree Foundation criticised the two bodies for failing to co-operate, and said that they should merge. The two bodies say there is no prospect of amalgamation.