The challenge to the status quo at one of Scotland's oldest public companies John Menzies has intensified with a call from the group's largest institutional shareholder for a review of its structure.

Kabouter Management, a US investor with a 9 per cent stake in the Edinburgh-based group, has questioned whether the dual business model created by Menzies 20 years ago is depressing the company's value.

It follows the emergence on Thursday of Swiss investment fund Lakestreet Capital Partners as a 3per cent shareholder with a public agenda to "unlock value" in Menzies.

The group's shares rose another 2.6 per cent yesterday, following an 8per cent jump on Thursday following the activist's initiative.

In an appeal to fellow investors, Lakestreet said it had met the company and "raised concerns whether keeping two non-synergistic businesses in one group is still in the best interests of John Menzies' shareholders".

Now Kabouter has revealed that its own research on Menzies concludes that the company's structure of operating in two unrelated sectors "contributes significantly to the undervaluation of John Menzies' stock today".

The US-based investor added that it was "constructive to have healthy dialogue that questions whether John Menzies was taking the right steps and exploring all options to unlock additional value", but stopped short of claiming to have been discussing those options with management.

However analysts point out that the Menzies family is still the group's biggest shareholder with a stake of over 10 per cent, while DC Thomson holds 8 per cent. In the recent activist challenge to Alliance Trust, DC Thomson gave its Scottish neighbour public backing.

Menzies shares jumped from 362.5p to 390p on Thursday after Lakestreet said it believed their real value was 86per cent higher or 675p.

However Panmure Gordon in a note by analyst Karl Burns said it believed Lakestreet's valuation of the aviation business was "overly aggressive", and he valued the shares at 401p. Brokers N+1 Singer have a price target of 391p on the shares. They closed 10.25p higher at 400.25p last night.

Panmure also says there is limited scope for value appreciation at Menzies' traditional newspaper and magazine distribution business, a market in structural decline, even if it were to spin out the business as WHSmith did with its former subsidiary Connect.

One analyst said he was surprised the move had come so soon after the installation of new chief executive Jeremy Stafford. "He has only been there six months and he is about to tell us about some new things they are doing - that might quieten everybody down a bit."

Menzies, founded in 1833, entered the aviation services market in 1995 after disposing of its Early Learning Centre chain and selling its heritage high street newsagent business to Smiths. It has always styled the dual business as covering "time-critical logistics".

The group took on debt to invest in ground-handling and cargo operations at airports around the world as it grew rapidly, but was punished when the shares sank to 43p in 2009 as investors panicked over its borrowings. However the stock then staged a remarkable comeback, climbing to a high of 825p by October 2013 before unexpected pressures emerged on margins, which alongside a restructuring at one of its biggest airport bases Heathrow prompted profit warnings last year and sent the shares plunging to 318p.