Software failures and a lack of capacity has caused mass lockouts from the MyGov online portal in recent weeks, according to users, with many clients staying blocked from the system for up to two weeks.

Users of the Commonwealth system are reporting  lockouts from accounts and shutdowns of the system with some clients taking their complaints to the Parliament and Commonwealth Ombudsman.

But the Department of Human Services continues to insist there is nothing wrong with MyGov except some problems in early July caused by an easily fixed algorithm glitch.

The denials come despite call centre operators telling callers in late July that a software problem had locked large numbers of users out of their MyGov accounts and that clients would have to wait 12 hours before they could log back onto the system.

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The complaints come in the wake of Commonwealth's new digital transformation boss' warning that the government was failing in delivery of online services to its citizens

A storm of criticism was recently aimed at the MyTax portal, linked to the MyGov system, for its performance at the end of the 2014-2015 financial year as millions of taxpayers tried to finish their tax returns.

Sources close to the portfolio have told Fairfax that "capacity issues" caused problems for MyGov, with pages not loading or sessions timing out within moments, late in June and that plans to add extra server capacity had been brought forward.

But a DHS spokesman denied there had been capacity problems with MyGov.

Victorian pensioner Vince Mahon has taken his complaint to the Commonwealth Ombudsman, saying he was one of many MyGov users locked out of their accounts in late July and their treatment was "unreasonable"

"I spoke to MyGov … was told defects in the software meant users in the last few days were locked out of their accounts," Mr Mahon wrote in his official complaint.

"The upshot is such users have to create a new account.

"MyGov does not have a procedure in place to reset your password.

"The problem was due to defective MyGov software but users are inconvenienced because there is no process to reset a password."

Sydney pensioner Rod Rodwell, who has taken his complaints to Minister for Human Services Marise Payne, told Fairfax of the difficulties in accessing MyGov in late June but said he and his wife had been struggling with the system for years.

"Our problems were around 22 to 24 June," Mr Rodwell said.

"Web page a disaster; there were queues at Brookvale because people could not get to page two.

"MyGov logins do not work; security codes issued do not work.

"Our experience over the last couple of years has rarely been different."

He said "Proxy Server errors" and "Service not available" were not uncommon.

Responding to question about the system's capacity, the DHS spokesman said that nothing was wrong.

"As we announced in the first week of July, the intermittent issues impacting some users trying to access the MyGov service and associated Centrelink online functions occurred from 1 to 3 July and have been resolved and were not related to capacity constraints," he said.

"The issues were quickly investigated and were resolved by adjusting our server routing algorithm."

The spokesman also denied software issues were causing lockouts from MyGov.

"There are no software issues with MyGov that result in accounts being unintentionally locked," he said.

"The system automatically locks accounts when there are nine unsuccessful login attempts in a row.

"This is a standard feature that has been built into the system in order to protect customer's privacy and security," the spokesperson said.