The retail property firm, which also owns Aberdeen’s Union Square, swung to a loss of £319.8 million in the six months to 30 June, compared with a £55.7m profit this time last year.
On an adjusted basis, which is the company's preferred measure, profits were down 10.5 per cent to £107.4m, while net rental income dropped 12.3 per cent to £156.6m.
The headline loss was largely down to a £423.4m net revaluation loss on its property portfolio in the first half, as continuing market uncertainty and a slowdown in leasing affected value, especially in the UK.
More than half of this was due to its flagship shopping destinations in the UK, which had a revaluation deficit of £266m.
In France, there was a revaluation loss of £71m, while the Irish portfolio was down by £30m.
However, premium locations produced a revaluation surplus of £111m.
Rental income on a like-for-like basis was down 0.1 per cent.
For UK flagship destinations the decline was steeper at 6.8 per cent, affected by company voluntary arrangements and administrations leaving shops empty.
Chief executive David Atkins said: "The UK retail landscape is undoubtedly challenging and traditional high street fashion is under pressure.
"However, our focus on shifting our line-up towards categories with greater customer appeal and rental growth potential has resulted in over 90 per cent of new leasing to leading consumer and food and beverage brands."
The group also said it had achieved 90 per cent of its target to sell off £500m worth of assets.
This included a £423m deal with AXA IM Real Assets for a 75 per cent stake in Paris's Italie Deux shopping centre, announced alongside the results on Monday.
Atkins said: "Our absolute priority remains to reduce debt. We stated our intention to achieve over £500m of disposals in 2019 and even in this tough environment where deals are taking longer to transact, we are now most of the way there.
"We will continue to pursue additional sales throughout 2019 and into 2020 to further strengthen our balance sheet."