Oct 21 (Reuters) - Dutch postal company PostNL warned on Friday that it expected a weaker third quarter and would not achieve its full-year outlook, sending shares diving 10% in morning trade.

The Amsterdam-listed group had cut its forecast in August for a second time, guiding for full-year normalised EBIT of between 145 million and 175 million euros ($142 million to $171 million).

"It is no longer realistic to assume that the current FY 2022 outlook for normalised EBIT (earnings before interest and tax) and free cash flow will materialise," it said in a statement.

PostNL, which delivers parcels and letters across Belgium, Luxembourg and the Netherlands, said a third-quarter return to volume growth had not materialised in its parcels division, blaming rising costs from high inflation and a tight labour market.

The Dutch firm now sees third-quarter revenues below its expectations at 709 million euros ($695 million), a normalised EBIT turning to a loss of 20 million euros and free cash outflow of 49 million euros.

Volumes are expected to be in line with 2021 in the fourth quarter, for it to be the strongest quarter and the "main driver for full-year performance", it added.

Capacity will be ramped up to almost double the usual number of parcels to be delivered for the period and higher hourly wages are on offer to ensure staff can cover year-end promotional periods such as Black Friday and Christmas.

Reports this week of the entry of Deutsche Post's logistics unit DHL in PostNL's Dutch home market drove shares lower on concerns of heightened competition. "We've not seen a deterioration of our market share position to DHL. But we need to be smart, we need to be careful and we'll be very selective," Chief Executive Herna Verhagen said in a call with analysts on Friday.

Shares of peers bpost, Deutsche Post and Österreichische Post also fell in morning trade after PostNL's profit warning. ($1=1.0205 euros) (Reporting by Elena Vardon and Piotr Lipinski; Editing by Jan Harvey and Clarence Fernandez)