John Menzies has said its £52million pension deficit could be a barrier to any plan to break up the business as proposed by activist shareholders.

The Edinburgh-based logistics group has disclosed a £12m rise in the deficit from £40m, alongside a six per cent rise in underlying pre-tax profit to £18.1m, helped by a big currency boost from the post-referendum fall in sterling for 80 per cent of its aviation earnings.

Chairman Dr Dermot Smurfit, appointed a month ago following shareholder pressure after Menzies lost its two senior executives and its chairman in quick succession, said: “We would expect our sales and financial performance to benefit should sterling remain at current levels or depreciate further.”

He said: “One of my tasks will be to review the structure of the group in order that we can maximise shareholder value. This will include looking at whether our two operating businesses are best placed to prosper while they are part of one group.”

Three shareholders –Chicago-based private equity group Kabouter Management, Swiss investment fund Lakestreet Capital Partners, and Frankfurt-based Shareholder Value Management - hold 27 per cent of Menzies between them, though are not acting together, and have called for the aviation and distribution arms to be spun off separately.

Dr Smurfit commented: “The situation is complex, particularly with regard to our pension schemes. Management have already engaged with specialist advisers and our pension trustees, and work is underway to structure the pension scheme in such a way as to give the board the maximum amount of flexibility in future. I expect this work to take up to 12 months and we will update shareholders when appropriate.”

Previous chairman Iain Napier had told shareholders that the board was unanimous in its view that the group could and should not be broken up.

On whether there was now a change of tone, company secretary John Geddes commented: “We have looked at it seriously a number of times, I think a change of chairman has brought a slight change in communications style. We do listen to shareholders, we are obviously going to look seriously and see if it is possible.”

Menzies operated without a chief executive from 2007 until 2014, then saw Jeremy Stafford resign last January after only 15 months. On whether he would be replaced, finance director Giles Wilson said: "We have the right team in place to support the business."

Underlying operating profit in the aviation division was up £1m to £10.4m, some £700,000 of it due to currency benefits. The group made 43 contract gains in ground-handling including a five-year contract with British Airways and Iberia at Copenhagen, and signed a joint venture in Oman for 50,000 turnrounds a year,

The distribution arm won its first national trucking distribution deal, with WH Smith for non-printed material, adding to three other contracts utilising its newspaper and magazine delivery fleet during daylight hours. The division's operating profit was £12m, down from £12.2m., though the Living Wage is now adding £1.6m a year to costs.