John Menzies is facing a renewed call to break up the group after a German activist investor increased its stake.

The £1.4 billion Frankfurt-based Shareholder Value Management has urged the Edinburgh-based logistics group to separate its aviation and distribution businesses, and accelerate the recruiting of an independent chairman, after taking its stake in Menzies to seven per cent.

SVM analyst Gianluca Ferrari said: “The sum of the values of the two businesses, taken separately, far exceeds the current market price.”

He said Menzies needed a new chairman to replace Dermot Jenkinson, 30 years on the board, who was appointed in May as interim chairman for 12 months, promising to lead the process of finding a new permanent chairman.

Mr Ferrari pointed out that Mr Jenkinson is connected to the founding Menzies family which still owns 19per cent of the shares.

The German move follows two similar activist calls last year, though SVM said it was acting alone.

In May 2015 Lakestreet Capital Partners, a Swiss investment fund which had acquired a 3.3per cent stake, urged the board to “unlock value” in the group with a demerger of the two divisions.

The following day Kabouter Management, a US investor with a 9 per cent stake, questioned whether the dual business model created by Menzies over 20 years ago was depressing the company’s value.

Since Lake Street emerged, John Menzies shares have risen by over 50per cent. They eased 3p to 552p yesterday, up around 11 per cent over 12 months.

A spokesman for John Menzies said: “We encourage an open and proactive dialogue with all our shareholders. In reference to today’s public statement, and as stated on 20 May 2016, the board is progressing its evaluation of the optimal structure for the group against the potential opportunities for expansion and acquisition in both divisions.”

In May 2015 the then chairman Iain Napier said the board had “decisively rejected” the call for a break-up, and had “condensed the previous two divisional management boards into one new executive leadership team". A new strategy to create a second growth business in distribution through parcels and e-commerce deliveries was being spearheaded by the then chief executive Jeremy Stafford.

However last January Mr Napier announced that £400,000-a-year Mr Stafford had resigned suddenly after only 15 months “for personal reasons”. He declined to comment further. Mr Stafford received a statutory pay-off of £65,200.

In March the group reported a 29 per cent fall in pre-tax profits and a 25 per cent earnings drop in aviation. It appointed distribution chief Forsyth Black to head the key aviation business and sit on the board, but made no reference to recruiting a new chief executive.

The group had returned to the three-director structure which it had operated for seven years until Mr Stafford’s recruitment, with finance director Paula Bell apparently restored to greater status and influence.

But in April Ms Bell, who succeeded long-serving Paul Dollman in May 2013, said she was resigning to join larger communications group Spirent in July as chief financial officer.

The annual report revealed that the disappointing aviation performance had led to Mr Stafford and Ms Bell receiving no bonus last year as pre-tax profit missed targets.

In May came the surprise announcement on the eve of the annual meeting that the £188,000-a-year Mr Napier, chairman since 2010, would be departing immediately, to be succeeded by Menzies family member Mr Jenkinson.