Babcock & Brown, Australia's second-biggest investment bank, has raised its stake in Britain's last remaining listed port operator, Forth Ports, to 20.4%.

The move has fuelled reports it could soon make a takeover bid for the docks' operator, which owns seven ports in Britain.

Forth Ports, based in Edinburgh, owns Scotland's largest container port, Grangemouth, and controls the Port of Tilbury on the Thames.

According to a report in the UK's Telegraph newspaper, analysts say Forth is now "in play" and predict a GBP1 billion-plus bid for the company that owns Tilbury Docks and has a substantial property portfolio.

However, one adviser in B&B's home city of Sydney says the investment is ""strategic" and unlikely to result in a takeover offer "any time soon".

The bank's listed infrastructure arm, Babcock & Brown Infrastructure, has maintained a breathtaking pace in acquiring assets in recent months, despite the rising cost of borrowing.

In August, BBI revealed it could spend more than AUD2 billion on acquisitions after reporting a 43% increase in pre-tax earnings to AUD513 million.