Royal Mail's owner said an increase in parcel deliveries over the Christmas period put it on track to return to annual profits as its £3.6bn takeover by Czech billionaire Daniel Křetínský nears completion.

International Delivery Services (IDS) said more than 99 per cent of Royal Mail mail sent on or before the recommended final delivery date over Christmas was delivered on time.

The 509-year-old postal company had struggled to deliver on time before the critical period but now says improvements to its operations will allow it to extend delivery hours to 9pm for the first time over the festive period. This enables Royal Mail to meet customer demand for next day delivery during peak shopping periods.

Royal Mail said there was strong growth in the number of parcels sent using its tracking service over the Christmas period, up 19% year-on-year to 188 million parcels.

Meanwhile, the company reported a 2.4% rise in revenue in the three months to the end of December, as it said its operating and financial results improved.

Royal Mail expects to return to adjusted operating profit (excluding voluntary redundancy costs) this financial year despite a "challenging macroeconomic backdrop". This comes after two consecutive years of losses.

The company said this provides "a solid foundation for future business development" ahead of the acquisition of IDS by Křetínský's EP Group.

In the three months to the end of the year, Royal Mail's parcel revenue rose by 3.2% and letter revenue by 1.4%.

The organization said the number of letters written fell again, down 7%, but this was offset by an increase in the price of stamps. In October, the price of first class stamps rose by 30p to £1.65.

Citizens Advice accused communications regulator Ofcom of "allowing the company to set soaring prices while failing to meet delivery targets for five years". Royal Mail also wants to reduce second class deliveries to rotating days to save costs.

The EP Group acquisition is expected to be completed by the end of March, following UK government approval in December last year.

Royal Mail's history dates back to 1516 and this will be the first time the company has been controlled by overseas owners.

After the takeover, the government will retain the "golden share" of IDS. This means any changes to Royal Mail's ownership, tax residence or headquarters will require government consent. The Royal Mail brand will also be protected as long as EP owns the company.

The deal has also received approval from European and U.S. regulators.

Martin Seidenberg, chief executive of IDS, said Royal Mail was "making more progress in adapting to customer needs".

"The successful enforcement of our union agreement has increased operational flexibility, which coupled with increased automation and thousands of new vehicles, has resulted in improved reliability," he said.

Seidenberg added that the company was working to mitigate inflationary pressures.

IDS said in November that an increase in employers' national insurance contributions set out in the autumn budget would increase its costs by £120m, and said it would not rule out cutting jobs or price increases to offset the hit.