LONDON (AP) – A British regulator said yesterday it is opening an investigation into the performance of investment banks in the lucrative business of underwriting corporate fundraising.

The Office of Fair Trading said underwriters earned an estimated £2 billion (nearly $3 billion) in supporting companies in raising £70 billion of capital for corporations in 2009.

Underwriters support share offerings – which may be flotations of a privately held company or a rights issue to raise money from existing shareholders – by guaranteeing that they will buy any shares not taken up. Two or more underwriters may club together in syndicates to provide this form of insurance.

Some companies have expressed dissatisfaction with these services, including the reported increase in fees. The Office of Fair Trading said its review will look at rights issues and other types of fundraising by the 350 largest public companies in the UK to consider whether users' concerns are justified.

Major underwriters in Britain include Barclays, Citigroup, Goldman Sachs and Royal Bank of Scotland.