The possiblilty of a four-way bidding war helped push LSE shares 21 pence higher in mid-morning trading to 573.00 pence.

In a statement to the Australian Stock Exchange - which was released in response to growing press speculation about a possible bid - Macquarie says it "is considering a number of potential acquisition opportunities which includes a possible formal approach being made to the London Stock Exchange".

The Sydney-based firm says deliberations are still "at the most preliminary of stages" but if any bid were made it would be as part of a consortium and "likely to be solely in cash".

The disclosure follows a Sunday Times report that Stockholm-based OM Gruppen is "sounding out advisers and potential partners" on a potential takeover bid for the LSE. OM originally launched a hostile takeover bid for the London exchange in 2000, which was branded inadequate by the LSE and also helped de-rail a potential merger between the UK exchange and Deutsche Börse.

The LSE rejected a second bid offer from Deutsche Börse in December last year which was worth around £1.35bn. The German exchange, which faced increasing opposition to its takeover plans from its shareholders, eventually ditched its takeover bid in March this year and later parted company with its CEO Werner Seifert.

Despite dropping its bid, the German exchange did leave the door open for a new approach, and its offer - along with that of its rival suitor Euronext - is still being investigated by the UK's Competition Commission, which is expected to release its conclusions in September.

However, the Commission has already raised concerns that a takeover of the LSE by either Euronext or Deutsche Börse would "substantially lessen competition", although it says it will engage with all parties in an effort to agree remedies to address the anti-competitive effect of a future merger.