Westpac Online Investing, has slashed brokerage rates to bring it in line with larger rivals Commsec and E*Trade in a bid to double its market share by mid-2013according to a report by the Australian Financial Review.

Clients who open a Westpac Cash Investment Account to settle trades will be offered a brokerage rate of $19.95, rather than the previous $24.95 rate, the report said.

In addition, clients who settle three or more trades a month will receive a variable bonus rate of 0.9 per cent, bringing its total rate to 5.65 per cent.

Currently, Westpac controls about 10 per cent of the online market, compared with about 50 per cent by Commsec and 18 per cent by E*Trade, according to the AFR.