Microsoft challenges Google with audacious $44.6bn bid for rival Yahoo

Microsoft, which came late to the internet advertising market, is offering Yahoo shareholders $31 a share in a combination of cash and its own stock. The deal would rank as one of the largest dotcom takeovers since AOL and Time Warner merged at the height of the tech stock boom.

The news boosted shares in London, sending the FTSE 100 back through the 6,000 level, and is expected to push Wall Street higher when trading opens later today.

There has been intense speculation about the two giants getting together. Microsoft has approached Yahoo several times over the past few years but been rebuffed. However Yahoo's position has weakened over the past few months as repeated delays to the roll-out of its new advertising platform Panama have sent its shares into freefall.