Staff process emergency and hardship grant applications at a Red Cross centre in Birmingham Dr in March 2011.

Families missed out on Red Cross hardship grants after the Canterbury earthquakes because a fraudster had already used their names and addresses.

That person was 40-year-old Donna Marie Nicola Paish, also known as Nikita Victoria Burns, who admitted 11 fraud charges in the Christchurch District Court on Monday.

Christchurch's city missioner said Paish had not only cheated a social services agency, but had taken money from people who were really in need.

The police summary of facts said between December 17, 2010, and March 28, 2011, Paish received a total of $17,000 from the Red Cross using seven different names and nine different addresses.

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The Red Cross described Paish's offending as a "regrettable and rare incident" and said it would investigate the matter.

After the earthquakes in 2010 and 2011, affected residents were able to apply for grants of up to $3000.

The money was for those who had to leave their homes, or endure living without power, water and sewerage in damaged properties.

Paish received four grants for $3000, five for $1000 and two of her applications were not approved.

The police said the actual occupants of the addresses were later declined grants because of her fraudulent applications.

Red Cross secretary general Tony Paine said those grants were in the context of more than $100 million paid out in Christchurch.

He maintained a high level of confidence in the organisation's system, but said issuing grants would always have a reliance on people's honesty.

"We will be investigating the specifics of this case carefully and if there are genuine people out of pocket because of [Paish] then we will remedy that."

Gorman said such fraud cases were "very upsetting".

Social agencies tried to put robust structures in place after the quakes, he said, but there was a fine line between verifying people's identity and being "overly intrusive".

Paish was already due to be sentenced on February 17 for other fraud offending, so Judge Brooke Gibson remanded her on bail to the same date for all matters to be dealt with together.

In 2012, Marie Elizabeth Hayward, 36, was sentenced on charges including using false documents for lodging three fraudulent claims with the Red Cross and obtaining $3000 after the February 2011 quake.