UPDATE 2-Kazakhstan says ENI, BG fixed costs to boost share

* Says costs overstated by $1.3 bln, reducing Govt take

* Govt wants stake of over 10 pct-sources

* BG denies any wrongdoing, says charges are not new

* BG says no progress on expansion of project

(Adds BG comments, sources on stake size, background)

By Raushan Nurshayeva and Tom Bergin

ASTANA/LONDON, April 29 (Reuters) - Kazakhstan, seeking a stake in a BG (BG.L) and Eni-led (ENI.MI) consortium developing the Karachaganak oil and gas field, increased pressure on it on Thursday saying the group had overstated costs by $1.3 billion.

The Central Asian state has in the past secured stakes in other energy assets owned by foreigners after accusing them of tax and environmental violations.

Kazakhstan's financial police said on Thursday the Karachaganak consortium, KPO, which also includes Chevron (CVX.N) and LUKOIL (LKOH.MM) had overstated its costs -- which are recouped from the government's share of project revenues.

"A new criminal case has been launched against the management of KPO BV over the theft of 187 billion tenge ($1.3 billion) by overstating its oil production costs by this figure in 2002-2007," financial police spokesman Murat Zhumanbai told reporters.

"This fact has been discovered by international audit companies KPMG and Ernst & Young and confirmed by experts."

"I can confirm to you very clearly that we have not overstated the costs," BG Chief Executive Frank Chapman told a conference call with reporters.

Chief Financial Officer Ashley Almanza, who is running the discussions with the Kazakh government for BG, added it was the same claim the government filed last year simply placed in a different form.

"There's a very constructive dialogue going on between the consortium and the Republic (of Kazakhstan)," Almanza said.

"The Republic has not made an offer to acquire a stake."

Nonetheless, Almanza said no progress had been made in the third phase of the project, which aims to lift output further and will require billions of dollars of investments.

A spokesman said the plans for the expansion were logged with the government and that the partners were awaiting a government response.

Even if the government agrees the expansion plan, BG and partners are unlikely to commit to any further investment until the current spat with the government is cleared up, Richard Griffith, oil analyst at Evolution Securities said.

GOVT SEEKS STAKE

However, sources close to the talks told Reuters Kazakhstan had made it clear it wanted a stake in KPO.

"We could be talking about 10 percent to 25-30 percent depending on the cost of the third phase," said a source close to the talks.

A source in the consortium confirmed that the government wanted more than 10 percent.

A spokesman from Kazakhstan's energy ministry declined to comment.

Analysts said the government was likely hoping to gain its stake without paying, possibly agreeing to drop its tax and cost claims in return.

The Karachaganak developments mirror the case of Kashagan, another oil field developed by foreign energy majors, where the government acquired a stake after accusing the consortium of environmental violations, delays and cost overruns.

Earlier this month, Kazakhstan accused KPO of violating immigration laws. [ID:nLDE635107]

In March, the financial police accused Karachaganak of illegally earning $708 million in 2008 by producing more oil and gas than originally agreed with the state. [ID:nLDE62P0WS]

BG reported a 5 percent drop in first quarter profits on Thursday, due to lower gas prices. [ID:nLDE63S075] (Additional reporting by Katya Golubkova in Moscow and Masha Gordeyeva in Almaty; Writing by Olzhas Auyezov; Editing by Jon Loades-Carter)