The company which cut the weight of Toblerone bars by widening the gaps between the chocolate peaks is now slapping a 20% price rise on Cadbury’s Freddo bars.

The recommended retail price of the chocolate frogs, which weigh 18g (0.6oz), is scheduled to jump from 25p to 30p in the spring. The US food manufacturing giant Mondelēz, which owns Cadbury, said it was having to make selective price increases as a “last resort”. The firm made a better than expected profit of $548m (£448m) in its last three-month financial period.

Other Cadbury’s chocolate bars are also expected to rise in price, but Mondelēz declined to name the other affected brands or say if all prices would go up by 20%.

Mondelēz, which also makes Ritz crackers, Philadelphia cheese, Oreos and Milka chocolate, said price hikes were necessary. A spokeswoman said: “Increasing prices is always a last resort, but to ensure we can keep people’s favourite brands on shelf and look after the 4,500 people we employ in the UK, we are having to make some selective price increases across our range.”

Economists have warned that inflation will rise in the coming months as a result of the decline in the value of the pound. Food manufacturers are either increasing prices or shrinking pack sizes – dubbed “shrinkflation” – as they look to maintain profit margins as input costs increase.

Shrinkflation started during the last recession and in recent years chocolate lovers have been regularly targeted: Mars and Snickers bars have got smaller; 1kg tins of Quality Street and Roses have slimmed down to 820g; and six-packs of Cadbury’s Creme Eggs – also a Mondelēz brand – have been whittled down to five.

Mind the gap: the new Toblerone bar comes with added space. Photograph: Darren Staples/Reuters

Mondelēz, which bought Cadbury in 2010, was widely criticised last year when it opted to widen the gaps between Toblerone’s chunky chocolate triangles rather than increase its price. Rival Mars has also shrunk its sharing bags of Maltesers by 15% as it looks for ways to offset rising production costs.

Mondelēz said rising commodity costs and recent foreign exchange pressures meant its food products were becoming more expensive to make. The pound has fallen sharply against the dollar since the vote for Brexit last summer. The company highlighted the price of cocoa, which it imports into the UK, had risen over 50% since 2013.

Earlier this week, Premier Foods, which makes Oxo cubes, Mr Kipling cakes, Bisto gravy and Homepride flour, said it was in talks with supermarkets over pushing up prices by about 5%. In the autumn Tesco had a public spat with Unilever over plans for price rises of up to 10% on brands such as Marmite.

A spokeswoman for Mondelēz said: “We have, and continue, to carry these increased costs within our business as much as possible, because our priority is to keep our brands as affordable as we can.” She added: “Importantly it is the retailer who ultimately sets the price on the shelf.”