British drugmaker Shire has rejected a £27 billion ($46 billion) takeover offer from AbbVie, the latest attempt by a US healthcare firm to tap into lower tax rates abroad via an acquisition.

Shire, which has no single controlling shareholder, has been seen as a prime takeover target for US drugmakers due to its attractive rare diseases business and its Irish tax base.

Saying its annual product sales are set to more than double by 2020 to $10 billion, Shire rejected the £46.26 per share offer as failing to reflect its true value, despite the offer being at a 30 per cent premium to its share price over the last month.

But analysts and one large shareholder said the firm may struggle to resist a bid of over 50 pounds per share.

"You can easily see other people coming for Shire now because it's in a good space," one of Shire's 40 biggest shareholders said.

Founded in 1986 in Britain, Shire conducts most of its business in the US and has been domiciled in Ireland for tax purposes since 2008.

AbbVie's takeover offer proposed creating a new US-listed holding company with a tax domicile in Britain, where the government has also introduced tax breaks designed to encourage research and development.

Ireland's corporation tax rate currently sits at 12.5 per cent, one of the lowest in the world, while Britain has been cutting its rate from 28 per cent in 2010 to 21 per cent this year and 20 per cent from 2015, well below the US headline rate of 35 per cent plus local taxes.-Reuters