Cairn's chief executive increased his stake showing confidence in the group in the same day that its Indian subsidiary was hit by a bill of at lest $1.6bn by the Indian government due to unpaid tax.Simon Thomson bought 50,000 new shares in the oil and gas exploration company for an individual price of 149.79p, spending a total of £74,895.After the transaction,Thomson holds 507,567 remaining shares.Shares in Cairn plunged by 16.6% on Wednesday after its Indian subsidiary, Cairn UK Holdings Limited, received a draft tax assessment order from the Indian Income Tax Department to pay $1.6bn plus any applicable interest and penalties.Thomson said: "Cairn has consistently confirmed that it has been fully compliant with all relevant legislation and paid all applicable taxes in India and we are confident of our position under the UK-India Investment Treaty."Top Director BuysKerry Group 'A' Shares (KYGA) Director name: Mr Philip ToomeyAmount purchased: 3,000 @ € 62.71 Value: € 188,130Cairn Energy (CNE) Director name: Mr Simon ThomsonAmount purchased: 50,000 @ 149.79p Value: £74,895Fidessa Group (FDSA) Director name: Mr John HamerAmount purchased: 2,000 @ 2,127.00p Value: £42,540Helios Underwriting (HUW) Director name: Mr Nigel HanburyAmount purchased: 20,000 @ 153.00p Value: £30,600Hardy Oil & Gas (HDY) Director name: Mr Alasdair LockeAmount purchased: 93,496 @ 30.75p Value: £28,750Alliance Trust (ATST) Director name: Mr Karin Forseke Amount purchased: 4,895 @ 490.24p Value: £23,997Galileo Resources (GLR) Director name: Mr Colin BirdAmount purchased: 985,000 @ 2.02p Value: £19,897Guscio (GUSC) Director name: Mr Marcus YeomanAmount purchased: 200,000 @ 8.00p Value: £16,000Hardy Oil & Gas (HDY) Director name: Mr Peter J MilneAmount purchased: 48,780 @ 30.75p Value: £15,000Waterman Group (WTM) Director name: Mr Craig W K BeresfordAmount purchased: 20,852 @ 71.50p Value: £14,909Top Director SellsNovae Group (NVA) Director name: Mr Matthew K FoshAmount sold: 79,007 @ 645.00p Value: £509,595Greggs (GRG) Director name: Mr Richard HuttonAmount sold: 26,750 @ 970.38p Value: £259,577Greggs (GRG) Director name: Mr Raymond ReynoldsAmount sold: 26,750 @ 970.38p Value: £259,577Greggs (GRG) Director name: Mr Roger WhitesideAmount sold: 12,251 @ 970.38p Value: £118,8814Imprint Group (FOUR) Director name: Ms Gillian DaviesAmount sold: 4,350 @ 990.00p Value: £43,065