FTSE flirts with record level though sterling boost fades; Inmarsat jumps

* FTSE 100 up 0.3 pct

* Inmarsat (Other OTC: IMASF - news) shoots up as SoftBank (Swiss: SOFB.SW - news) speculation swirls

* 3I tops FTSE after Barclays (LSE: BARC.L - news) upgrade

* Polls send sterling lower, boosting large-caps (ADVISORY- Follow European and UK stock markets in real time on the Reuters Live Markets blog on Eikon, see cpurl://apps.cp./cms/?pageId=livemarkets)

By Helen Reid

LONDON, June 1 (Reuters) - Britain's major share index climbed on Thursday, flirting with its record high level but underperforming European peers, while Inmarsat rose on merger speculation.

The FTSE 100 was up 0.3 percent, with consumer staples and industrials stocks providing the top boosts to send it hovering near its highest intra-day level of 7,586.45 points hit on Wednesday.

A weaker sterling initially provided a boost to the London-listed multi-national firms, but the currency turned positive by the end of trading. Pressure on sterling has been intensifying over the past week as some opinion polls point to a tighter-than-expected race.

The latest poll published by the Times showed May's lead down to just 3 percentage points ahead of the opposition Labour party, with a week to go until the vote.

While the large-caps were ahead on the day, they underperformed the broader European index and were handily beaten by French and Italian equities.

UBS Wealth Management warned that the boost to the FTSE 100 from the weak pound could be turning stale.

"The UK equity market's tailwind from the weak pound is fading, and as we lap the currency low point during the second and third quarters of this year, the market will no longer receive a boost from currency effects," said deputy head of the UK investment office Caroline Simmons.

Mid-caps, which have been outpacing their larger counterparts, lagged slightly, up just 0.2 percent.

"We have seen a relative underperformance of domestic-focused UK equities as political risk increases alongside the perceived uncertainty of the Brexit outcome," said Edward Park, investment director at Brooks Macdonald (LSE: BRK.L - news) .

But Inmarsat gained 5.4 percent on the day, leading the way among European satellite companies, with France's SES and Eutelsat (Paris: FR0010221234 - news) also fuelled by speculation they could be takeover targets after sources said Softbank would let its planned $14 billion merger between OneWeb and Intelsat collapse.

Gains among large-caps were broad-based and broker calls helped some specific stocks stand out.

Private equity (IOB: 0QLS.IL - news) firm 3I Group rose 3.2 percent after Barclays raised its price target on the stock, saying a trading update from Action management, which accounts for 30 percent of 3I's portfolio, was reassuring and the group was confident on cash generation.

Mediclinic however sank 3.4 percent, the top FTSE faller, after both Credit Suisse (IOB: 0QP5.IL - news) and Bank of America Merrill Lynch cut their rating on the private health-care provider.

Meanwhile mid-cap bus and rail company FirstGroup (Amsterdam: FI6.AS - news) fell 5.7 percent after a 23-percent profit jump was overshadowed by its warning of a mixed trading outlook.

Challenger bank Aldermore fell 3 percent after Exane cut it to "underperform", citing slowing loan growth and an uptick in impairments.

Online car retailer Auto Trader (Frankfurt: 2UA.F - news) hit a record high after Barclays upgraded the stock to "overweight." Its shares were up 4.5 percent.

National Grid (LSE: NG.L - news) , Taylor Wimpey (LSE: TW.L - news) and Marks & Spencer had all gone ex-dividend on the day.

Business support services firm G4S (Copenhagen: G4S.CO - news) and real estate investment trust Segro (Frankfurt: S4VC.F - news) were confirmed as the latest additions to the blue-chip index, with changes effective on June 16.

Intu Properties (LSE: INTU.L - news) and Hikma Pharmaceuticals (Frankfurt: A0HG69 - news) were set to be demoted to the mid-cap index, as part of the quarterly review reshuffling stocks based on their relative size. (Reporting by Helen Reid; Editing by Andrew Heavens)