Greater Wellington Regional Council has requested its chief executive to meet KiwiRail to discuss upgrades to the Wairarapa rail line.

An urgent push to upgrade Wairarapa's ailing rail line is set to begin as commuters continue to be frustrated by frequent delays and disruptions.

The Wairarapa service has been notorious for lateness in recent years, mainly due to its ageing tracks, which mean trains are subject to speed restrictions.

Reliability has become so bad that only 64 per cent of trains arrived on time between July and May, a decrease of 18 percentage points over the previous 12 months.

ILLYA MCLELLAN/STUFF The Wairarapa line has been dogged by lateness and overcrowding for several years.

While the Government announced improvements to the similarly ailing Hutt Valley line as part of a $98 million Budget funding boost in May, the Wairarapa line was not so lucky.

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Greater Wellington Regional Council chief executive Greg Campbell said councillors were growing impatient with the situation, and that had led to them requesting he meet track owner KiwiRail to seek an explanation for the poor performance.

SUPPLIED Greater Wellington Regional Council chief executive Greg Campbell. Councillors were growing impatient with the lack of progress on the Wairarapa line, he said.

The council has also passed a recommendation requesting Campbell begin discussions with KiwiRail, the Ministry of Transport and Wairarapa MP Alistair Scott about upgrading and maintenance of the Wairarapa line.

It has also asked Campbell to meet train operator TransDev to discuss overcrowding on the Wairarapa line.

The recommendations were partly spurred by the Government's Wairarapa line snub, with councillors not wanting to wait until next year's Budget to receive possible funding, Campbell said.

"I think the frustration is that the standard process is we'll do a submission, probably later this year, which will feed into the formulation of the following year's Budget.

"That means we could potentially only get a Budget vote this time next year, which means probably another year to do the work. And what's going to happen to these commuters?"

The council had expressed a "sense of urgency" about confronting KiwiRail, but it also understood the problem was a major infrastructure investment issue, "and there's no easy answer to that", Campbell said.

"This is really saying, 'We need that investment earlier than two years' time on the Wairarapa line'.

"I can't pre-judge a KiwiRail or central Government decision, but I can certainly put a good fight forward."

KiwiRail said on Wednesday: "We work very closely with Greater Wellington and Transdev at all levels, and there are regular meetings, including between the chief executives, regarding the operation, maintenance, renewal and upgrade of the Wellington network.

"Funding for public transport, including the cost of renewing and upgrading the line, is primarily an issue for Greater Wellington, but we are working together constructively to ensure the best possible service is offered on this line."