LONDON March 27 - The grocery market share of Tesco Plc, Britain's biggest retailer, is still falling, while No. 2 player Asda's is at a record level, industry data showed on Tuesday.

Market researcher Kantar WorldPanel said Tesco's market share fell 0.4 percentage points year-on-year to 30.2 percent in the 12 weeks to March 18.

In contrast, the share of Asda, owned by U.S. firm Wal-Mart Stores Inc, rose 0.6 percentage points to 17.9 percent, reflecting the full integration of Netto stores acquired last year.

Tesco issued its first profit warning in living memory in January and earlier this month parted company with the CEO of its UK business, Richard Brasher.

The later announcement came 10 days after Tesco detailed a programme to invest in existing and new stores and take on 20,000 new staff.

Kantar said Tesco's sales growth was 2.7 percent in the 12-week period, lagging market growth of 4.0 percent but an improvement on growth rates seen so far this year. Asda saw sales growth of 7.8 percent.

The share of Sainsbury, Britain's third-largest grocer, and Morrison's, the No. 4 grocer, were unchanged at 16.6 percent and 12.3 percent respectively.

Last week Sainsbury beat forecasts for fourth quarter sales.

Kantar said Waitrose, the upmarket grocer owned by John Lewis, and discounters Aldi and Lidl, all continued to outperform the market, as did frozen food specialist Iceland.

The overall market growth of 4.0 percent in the latest 12-week period represents a slight slowdown from growth of 4.5 percent in the 12 weeks to February 19 and is below a grocery inflation rate of 5.5 percent.

Kantar said this meant shoppers were taking advantage of the current crop of special offers.

Separately on Tuesday a survey by the Confederation of British Industry (CBI) said retail sales unexpectedly steadied in March, although stores did warn that high fuel prices and slow wage growth meant the outlook was poor.

(Reporting by James Davey; Editing by David Holmes)