Assura's major shareholders have opposed a tie-up with a US private equity giant.

Top ten investors Quilter Cheviot and Schroders, which own around 6 per cent and 5 per cent of shares in the NHS landlord respectively, favour a deal with London-listed rival Primary Health Properties (PHP) over US buyout giant KKR.

Allianz, Gravis, Baillie Gifford and Columbia Threadneedle have also leant their support to PHP’s bid.

Shareholders argued that KKR’s proposal undervalues Assura, which owns GP surgeries, hospitals and hospices across the UK.

A deal with KKR and its partner Stonepeak would see buildings leased to the NHS fall into the hands of overseas owners. 

But a takeover by PHP would retain the properties under the ownership of a London-listed business.

Assura this week said it would weigh up an improved bid from PHP, despite having backed KKR’s £1.7billion offer last week. 

Marcus Phayre-Mudge, manager of Columbia Threadneedle’s TR Property Investment Trust, said: ‘The KKR bid simply doesn’t offer a premium significant enough to justify walking away from this long-term opportunity.

‘That’s why we strongly support the PHP-Assura merger and encourage other shareholders to do the same.’

A Gravis fund manager said PHP’s offer was a ‘superior choice for long-term investors’. The KKR bid ‘risks crystallising value at what may be a cyclical low’, they added.

Baillie Gifford investment manager Jon Stewart said the KKR deal was not ‘in shareholders’ best interests’ and ‘undervalues Assura’s long-term growth potential’.

KKR’s ‘best and final’ bid values the company at 52.1p per share, although that includes already declared dividends. Without those, the offer is worth 50.42p, analysts said.

Most recently, PHP offered £1.68billion to buy Assura but argued last week that its cash and stock bid is worth more as the value is based on share prices. Assura shares slid 0.1 per cent, or 0.05p, to 50.1p.